Jun 132012
 

Potatoes, fresh from the ground, prior to being cured then stored.

Potatoes are an excellent crop to grow, and to store.

Probably no other crop yields as much protein, or as many calories, when measured against the hours of work it takes you to grow, care for and harvest them.  Potatoes yield more calories per square foot of growing space than anything else, and more protein than anything except for legumes.

Depending on the soil and your growing strategy, you can expect yields from about 1.25 lbs per linear foot of potato row up to 4 lbs or more per linear foot (ie between about 20,000 and 70,000 lbs/acre – national commercial average of 41,300 lbs/acre).

Originating in South America, potatoes were brought to Europe in the late 1500s.  They have steadily grown in popularity and now are the world’s third largest cash crop (after rice and wheat).

Potatoes don’t need a lot of water or fertilizer.  And if stored in optimum conditions, you can get as much as ten months of storage once you’ve harvested them.  They can be grown across much of the US, and although they prefer cooler climates, they are even grown in Florida and Arizona.  They are grown commercially in 36 of the 48 Conus states.

Potatoes are also a key source of nutrition for most of us.  On average, Americans each ate 117 lbs of potato in 2010.

That’s not to say that potatoes are a perfect crop.  Of course, some environments are not suited for potato growing (and different types of potatoes grow better/worse in different conditions), and equally of course, as students of history will know (the various Irish and Scottish potato famines in the 1840s and 1850s) they are vulnerable to some types of bio-hazards (particularly viruses and pests) that can destroy entire growing seasons worth of potatoes.

As with anything else, we always encourage you to diversify the food products you grow so if one crop has problems, you will hopefully still have other crops unaffected by the problems impacting on the challenged crops.

But those considerations are for another time.  Tis article starts at the end of the growing of potatoes, and assumes you have already carefully harvested them at the ideal time.

There are four considerations to keep in mind when storing potatoes.  They need to be kept cold, dark, humid, and with a small amount of air circulation.

Remember that the harvested potatoes remain as living things.  They are made up of about 80% water and so need to be in a humid environment to prevent them drying out.  The cooler they are kept, the slower their ongoing aging will be, and keeping them out of the light will prevent the light stimulating the formation of bitter-tasting and poisonous glycoalkaloids.

Let’s look at their storage requirements step by step.

1.  Preparation for storage.

You should avoid washing the potatoes (ie keep them dry) unless absolutely essential.  If you must wash them, do so gently and not physically damage the potatoes (they are reasonably vulnerable to damage until their outer skin has a chance to harden) and ensure they are well dried.

It is recommended you should dig up the potatoes after a few days of dry weather, so they will be dry to start with, and leave the potatoes out in the field for a couple of hours so as to dry them further and to make it easier to clean them by brushing any dirt off them.

Treat potatoes as reasonably fragile before they have been cured (and still treat them carefully afterwards too).

2.  Curing the Potatoes

Before putting the potatoes into ‘deep sleep’ you first want to encourage them to adjust to their now out-of-the-ground experience.  You do this by curing them for a week or two, in a well ventilated humid and dark place, at a temperature of about 50 – 60 degrees, or a shorter time at a warmer temperature (ie 5 – 10 days at 59 – 68 F).  This will toughen up their skins and might help any harvesting damage to heal.  Humidity should be about 95% – 98% – as humid as possible without condensation forming.

3.  Storing the Potatoes

At the end of the curing process, you will want to inspect all the potatoes again, and if they are satisfactory with no sign of any type of infection or damage, transfer them to long-term storage.

This will also be in the dark, and also be very humid – as before, as humid as possible without allowing any condensation.  Actual water will cause the potatoes to rot.

Temperature is ideally cool to cold, but no colder than about 39 F.  If you plan on frying the potatoes, you might want to keep them a bit warmer – perhaps no cooler than 45 F.  Colder temperatures accelerate the speed of starches converting to sugars, and while in some vegetables, a sweetness is desirable, it tastes strange in potatoes.  Furthermore, if you then fry the potato, the sugars would burn.

Warmer temperatures encourage the potatoes to sprout and also accelerate the development of tuber diseases.

There should be a little air flow to enable the potatoes to ‘breathe’.

Be careful what else might be stored in the same area, or sharing the same air.  Some produce gives off ethylene gas which massively reduces the storage life of potatoes.  And the subtle smell given off by stored potatoes can be taken up by apples and gives them an unpleasant flavor.

Don’t store the potatoes piled too high – not only does this reduce the air flow into the potatoes in the middle of the store, but it also puts harmful pressure on the lower potatoes that might damage them.  It is suggested not to have potatoes piled more than 2 feet high.

From time to time during their storage (ie about once a month – more regularly if you are having storage problems) you should inspect them for signs of any rot or infection.  Remove any that show any signs of problems, before they start to infect other potatoes close to them.

Some people suggest removing adjacent potatoes if you find a potato that is going bad.  In a perfect world, this makes sense, but you need to trade-off between, on the one hand, disposing of too many potatoes unnecessarily just because of their proximity to bad potatoes, and on the other hand, of not throwing away infected potatoes that quickly get worse and pass the infection further on into your potato stock.

Probably what we’d do is create two supplementary storage places in your potato cellar.  One for actively going bad potatoes, and we’d eat those first (well, not the bad bits, of course).  Then the second storage place would be for suspect potatoes, and we’d eat those second, leaving the main bulk of the potatoes in the normal storage area(s).

Seed Potatoes

Store seed potatoes at a colder temperature than ones you plan to subsequently eat.

You can take seed potatoes all the way down to almost freezing.  You also want to keep the humidity high for them, too, but with seed potatoes a pale diffuse ambient light is recommended.

The Greening of Potatoes

When potatoes are exposed to the light, two things happen.  A green layer forms on the exterior of the potatoes, and glycoalkaloids are formed inside the potato.

Glycoalkaloids (in particular, solanine) are both bitter and poisonous.  All potatoes have a low level of glycoalkaloid in them, and they help to give potatoes their distinctive flavor/taste.  Light exposure causes more glycoalkaloids to form.

Some people think the green they see contains the glycoalkaloids.  This is not so – the green is harmless chlorophyll.  And so simply peeling off the green layer does not make the potato safe to eat.  The green chlorophyll is merely an indicator that correlates to the level/presence of glycoalkaloid in the potato as well.  If you see a lot of green, dispose of the potato and don’t eat it.

Even a day of sunlight can be enough to push glycoalkaloids up to unacceptable levels (something to think about next time you visit a farmers’ market in the summer and see stalls with displays of potatoes sitting in the sunlight).

Less than Optimum Storage Conditions

Not everyone will have a perfect potato store-room.  The key things for you to consider when storing potatoes are keeping the temperature as cool as possible, but generally above about 40 degrees, and to ensure there is no light in the storage area.

The next thing to optimize would be the humidity – the more the merrier – and a little bit of air flow.

Also, remember to check the potatoes when first storing them.  If they are your own potatoes, clean and cure them first, be sure they are dry, and remove any ones with any signs of infection.

A day of bright sunlight is enough to spoil a potato, so darkness is most important.  As for temperature and humidity, the warmer the temperature, the quicker the potatoes will age, and the drier, the more the potatoes will shrivel up.  Sprouting is usually the first sign of potatoes being stored too warm, and shriveling a sign of insufficient humidity.

You’ll see a number of internet sites with various suggestions about how to store potatoes if you don’t have a temperature and humidity controlled cellar.  Some of these sites have conflicting and even close to contradictory ideas; the kindest reason we can think of for this is that they are recognizing the compromises that have to be made and are more concerned with extending potato life from a week or two (if not stored well) up to a month or two (in slightly better conditions).

Boxes lined with straw or peat moss are a common theme.  If you do this, remember the need for potatoes to breathe and to get some fresh air, and also remember that while it is okay to keep the potatoes humid, you don’t want to get them actually damp/wet.

If nothing else, keep them in the coldest part of your house, and block the light from reaching them.

Some root vegetables allow for very simple storage – simply leaving them in the ground.  This is less appropriate for potatoes.

Summary

The humble spud should be an integral part of your food growing and storage plans.

It has everything going for it – reasonably easy to grow, gives a good food yield in terms of the amount of man hours needed to put in to growing them, is nutritious, and can be stored for up to 10 months.

The closer to our optimum storage guidelines you can get, the longer the storage life and the better the potatoes will be when you eat them.

May 262012
 

Water is life, particularly after a Level 2/3 event.

Finding the ideal retreat location is a bit like finding the ideal spouse.  Almost impossible.

There are many different factors to consider in evaluating different retreat locations, including for most of us the key issue of affordability (although when it comes to Level 3 scenarios, it could be argued that a bad retreat location is only slightly better than no retreat location at all).

How to juggle the many different factors for a ‘perfect’ retreat (or, better to say, a ‘least imperfect’ one) involves trying to balance out the different issues, and accordingly different priorities to each issue.  For example, it may be helpful to be close to a railroad track (our guess is that in a Level 3 scenario, trains will start long distance freight and passenger service long before regular road vehicles).  But would you rather be close to a rail line or a river – both may offer transportation options, and a river has another possibly vital plus point too.

Which brings us to the content of this article.  The essential importance of a water supply at your retreat location.

Many Different Uses of Water

Now you probably already know that you need water, right?  You know, that thing about dehydration being fatal after three days with no water, and the rule of thumb about allowing a gallon of water a day for essential minimal uses.  But that’s not the end of the story.  It is barely the beginning of the story.

For a Level 3 scenario, you don’t just need a gallon of water a day – you might potentially need 1,000 gallons a day (to water crops and feed animals) or even more (to run a micro-hydro power station), as well as the modest quantity for yourself.

Let’s think about all the ways that water can help you :

Drinking water – Must be free of contamination, only needed in low quantities

Other Household water – For cooking/washing/flushing type purposes – of successively lower quality

Agricultural water – Some bio-contamination fine, but free of chemicals and poisons, needed in potentially large quantities

Power – Hydro-electric power requires freely flowing water running down a grade, watermills can work on lower flows and lesser drops; needs huge quantities of water

Food – Lakes, rivers and streams could be sources of fish, a more ambitious project is to consider aquaculture

Transportation – Some rivers and lakes are navigable, and water transport is energy-efficient (particularly sail powered)

Security – A water obstacle won’t necessarily make it impossible for attackers to reach you, but it will slow them down and make them more vulnerable while crossing it

Fire-fighting – If you should have a fire, you’ll need a plentiful supply of water to fight it

Money – Maybe you can sell water to others

Community – See our last point, below.  Becoming the community water source helps the community coalesce.

So water is a vital resource, and easy access to large amounts of it – large amounts that don’t require major energy costs to retrieve – is a very important part of choosing your retreat location.

You need to think beyond the simple ‘can I get my gallon of water a day’ concept and consider issues that might require tens of thousands of gallons of water a day, such as the ‘bonus’ of being able to use a water source for hydro-electric power generation.

A further bonus is the potential for catching fish and providing food.  With so many people talking about ‘I’ll go out and hunt deer’, we wonder just how scarce wild game may become; but if you have access to a reasonably private lake or river, maybe your fish supply will not be so threatened.  Maybe.

Many Different Sources of Water

So where can you get water from?  Many different places is the happy answer.

Rainwater – an unreliable seasonal source, better in some areas than others, possibly sufficient for basic household needs.  Almost always of very high quality.  Requires potentially extensive (and therefore expensive) storage capacity so as to keep it available for use in dry months.

Free-flowing springs – These are wonderful but rare.  If you can come up with a spring/well where the water comes out of the ground ‘all by itself’ you are extremely blessed.  Need to check the water quality, and confirm the reliability of the spring flow year-round, and from one year to the next to the next.  Assuming reliable and adequate flow rates, no need for storage.

Wells – These can be prodigious sources of water, but require energy to lift the water up from the level it is found in the well.  We discuss this in our article The Energy Cost of Pumping Water from a Well.  More likely to be reasonably pure, but need occasional testing.  Assuming reliable and adequate flow rates, no need for storage.

Rivers and streams – Possibly of varying reliability.  May freeze over in the winter and dry up in the summer.  Will probably require energy expenditure to transfer water from river/stream to retreat.  Of uncertain purity, and need ongoing testing to keep on top of changes in the water quality.  Assuming the water is available year round, no need for storage.

Restrictions on Water Use

The more arid the state, the greater the legislative focus on the ‘ownership’ of water.  And also the ‘greener’ the state (ie the more eco-focused) again the greater the focus on leaving water flows undisturbed.  The welfare of fish is considered more important than the welfare of the state’s citizens.

Restrictions may exist at a state-wide level or at a county level – possibly even at a city level.  Bearing in mind our strong suggestion that everything you do be fully compliant with all current laws, you need to be aware of possible restrictions on your use of water that flows through or near to your property.

City Water Supply

We hopefully don’t need to tell you this, but if you are at a location which provides city water, you should not base your retreat planning on the assumption that the city water supply will continue uninterrupted WTSHTF.

While there is a temptation to using the very inexpensive city water prior to a Level 2/3 event, we recommend you use your own water supply right from when you set up your retreat.  This will give you a chance to identify any problems and issues, and will give you the opportunity to resolve them while you still have all the wonderful resources of modern civilization at hand.

If you just sink a well then leave it, untouched, for years, while happily using the city water instead, you have no way of knowing if something has happened to the pump or maybe the water table has lowered and the well is no longer able to supply you with water.  It is probably better to use your well and pump on a regular basis than to leave it unused and have parts dry out or rust up or whatever else.

Selling Water – Building a Community

You should get a feeling for how other people in your general area get their water.  And think it through to ‘could they continue to get water from this source WTSHTF’.  If everyone has wells, the question becomes ‘Do they have storage tanks, and do they have some way of powering their pump’.

If you live a long way from your nearest neighbor, and if there are some hundred feet of altitude separating you from your neighbors too (especially if you are lower) then maybe you would not be a convenient source of water, especially if there was a good river running by closer to them.  But if water is in short supply, and if you have an abundant source of it, then maybe you can make money by selling water to your neighbors.

We’d suggest you not be greedy in such a case.  You obviously need to cover your energy costs, and the time/hassle factor.  Beyond that, though, being able to help your local community provides a common tie to unite you all – the need to protect your water source from outsiders.  That’s an obvious benefit to you, as is anything that helps a community work together and to establish their self-sufficiency.

How should you be paid for the water you sell?  That’s an entirely different topic, and it depends on the likelihood of the dollar staying as the currency of the country when life returns back to something close to normal.  It also depends on what you most need and what the people buying the water from you have the most of.

If you are using diesel to drive a generator to power the water pump, maybe you say ‘500 gallons of water for one gallon of diesel’.  That sounds very fair, but with your underlying ‘cost’ of diesel to pump the water being more like one gallon of diesel for 7,000 gallons of water, you’ve not only covered the cost of the water, but more than 7 of the 8 pints of diesel you received in exchange can be used for powering other things for other purposes, too.

If you become the community water supply, you could also become the community trading post for other things too – you could even allow (encourage) your neighbors to set up stalls selling and trading the foodstuffs and other items they have for sale in exchange for things they need.  It makes you a community leader, and helps encourage the community to in turn protect and assist you.

May 172012
 

When all else fails, a hand operated pump may yet become necessary!

If you have a well, you need a pump to do two things for you – one obvious, the other perhaps not quite so obvious.

First, you need to pump the water from whatever level the water table is underground up to the surface.  Second, you need to then pressurize the water for ongoing distribution from the well-head.

Considering the second point first, home water pressures are typically in the range of 30 – 80 psi, with 45 – 60 being considered optimum.  Each pound per square inch (psi) of water pressure is equivalent to raising the water 2.31 ft, so a 20 psi pressure can be thought of as the same as adding another 46.2 ft, 40 psi is more like another 92.4 ft, and 60 psi is 138.6 ft.

So simply add however many feet of desired ‘pressure equivalent’ to the depth the water is at to find a total water lifting height.  We recommend you consider a lower pressure rather than a higher pressure – sure, your showers won’t be quite so wonderful, but your plumbing system will be less stressed and less likely to leak – probably a more than satisfactory trade-off for most of us.

In a perfectly efficient pumping situation, you would be able to lift 319.5 gallons one foot by using one Watt hour of power.

But pumps are rarely perfectly efficient.  Typical efficiencies range from around 40% up to about 70% in the best case scenario.  Smaller pumps are typically less efficient than larger pumps.  If we aim for 55% as a mid point, this suggests 175 gallons can be lifted one foot with one Watt hour of power.

Note – usually efficiency trade-offs are balanced in part by cost considerations (the other part being unavoidable design issues), and these considerations are based on an assumption that energy is freely available and affordable.  Neither is a valid assumption in a Level 2 or 3 scenario, so we urge you to pay extra up front for the best efficiency possible.  A more efficient system in any scenario might have an impractically long apparent pay-back period in today’s situation, but when your energy becomes in short supply and massively more precious than it is today, the pay-back periods will become very short indeed.

If you have a 100 ft deep well, and if you want to pressurize your water to a bare minimum of 30 psi (ie another 69 ft of lifting), each gallon of water you pump will require almost exactly 1 Watt hour of power (assuming the 55% efficiency).  You could pump 1000 gallons for a kWh of power.

Here’s an excellent explanation of how these figures were derived.

So that is the energy cost of pumping water – about one kWh for 1000 gallons lifted 169 ft (a combination of well depth and pressure height) in a realistic type of scenario.  More lift means more energy, of course.

In an off-grid situation, where are you going to get that 1 kWh of energy from?  Let’s see what it might require in meaningful terms.

Solar Power

A 10 sq ft solar cell array would generate about 100 – 125 Watt hours in an hour of bright sun; allow for inefficiencies in converting to battery power or whatever else, and say best case scenario is 100 Watt hours per hour of direct sun.  So this one solar cell array would provide sufficient power to pump 100 gallons/hour of water in bright sun.  In not quite so bright sun, of course, you’ll get less energy and it will take more hours of ordinary obscured sun and cloudy days to generate the same amount of accumulated Watt hours of power.

You’d need to work out how many gallons a day of water you need to be able to pump, and match that to a suitably sized solar cell array; and probably you’d add some storage – either battery or water to balance out between bright sunny days and dark cloudy days.  On bright sunny days you’d either divert the extra energy into a bank of batteries or simply pump more water than you consume, storing the surplus in tanks, and on dark cloudy days you’ll either run the pump from batteries or take your water from the tank storage.

Our personal preference is to store the surplus energy in the form of water in tanks.  It is the simplest and lowest-tech solution, and there is much less to go wrong and fewer inefficiencies in having water sitting in a tank than in having electricity being converted into and out of a bank of storage batteries.

Generator Power

If you were running a diesel generator, a rule of thumb is that a gallon of diesel will convert to about 10 kWh of energy.

Allow for inefficiencies in storing the electricity from the generator into and out of a battery bank, and say perhaps 7 kWh net of energy from a gallon of diesel, which means a gallon of diesel will be good for about 7,000 gallons of water pumped.

A gasoline powered generator would deliver appreciably fewer kWh of energy per gallon of gas, and is also less reliable, so we generally don’t recommend gasoline generators.

Alternatively a diesel powered water pump could be used at the well.  You’d have fewer energy conversion losses and might get better efficiency, closer to the 10 kWh of energy per gallon theoretical maximum, but this gives you another diesel motor to maintain and care for, adding to the complexity of the equipment you have at your retreat.

The other consideration of course is that sooner or later, you will run out of stored diesel and may not be able to replace it, while the sun will continue shining hopefully for as long as we need it to.

Summary

Well water is not ‘free’.  It has a clear energy cost associated with it, depending on the depth of your well – the deeper the well, the greater the energy needed to lift the water up to the surface and to pressurize it for distribution.

Fortunately, the energy required to bring water to the surface is not excessive.  Depending on the amount of sun where you live, a solar cell array that probably costs $1000 or so would be enough to power a pump capable of giving you several hundred gallons of water on most average not-too-cloudy days, and some storage tanks for the pumped water would give you a store of water for cloudy days when insufficient water could be pumped by the solar powered pump.

May 162012
 

Rainwater tanks come in all colors, shapes, sizes, and materials.

Storing rainwater of course has cost associated with it.

You’ll want to store enough to make sense, but not too much.  There’s another issue too – in some drier areas, the amount of water you need for the dry months exceeds the amount of water you can collect and store in the wet months, so you need to calculate both the amount of water to store and then to confirm you’ll actually be able to collect that much during the wetter months.

Sadly, the final calculation is not as exact as it might seem.  Sure, you’ll have surrounded yourself with vast masses of rainfall data as part of your calculating, but as you’ll see from the worked example below, at the end of the process, you end up making some subjective guesses.  Feel free to ask us if you have questions or need help.

Getting the Raw Data You Need to Do Your Calculation

The key issue now is understanding the rainfall pattern you’ll experience at your location.  This involves both some science and some art.

The science is simply retrieving historical rainfall data.  The art lies in translating historic rainfall data, which varies from year to year, into the acceptably likely/moderately worst case scenarios that you want to build into your planning, and in taking rainfall data from weather stations that might not be close to your location and equating their rainfall data to what will actually happen at your location.

It is an easy thing to go to various different websites and get average monthly rainfall data for a range of different locations around the country.  We have some links in this article, just a bit further down.

Equating Rainfall at Weather Stations to Rainfall at Your Location

So how to equate this rainfall data with what happens where you are.  Maybe you are 50 miles away from where the nearest data is collected.  That could be okay, but maybe you’re in the rain shadow on the other side of a mountain range from where the data is obtained.  Ooops.  That’s not going to work, is it!

So find the best data you can, and if you can’t find any good data, maybe consider averaging the data from several reasonably close locations.  It is better than nothing.  In particular, use the National Weather Service rainfall maps (link below) to get a sense of the rainfall patterns and distributions for where you live compared to where the sampling stations are.

You can also ask local residents for reality checks about what they might remember or have recorded for past years.  Perhaps they can at least answer some simple questions like ‘how often is there no rain at all in July’ and ‘what is the longest gap between decent rains’ and ‘which month do you need to water the crops the most’.

If you want to get really obsessive, you can even go to the archives of the local newspaper and track daily weather from back issues of the paper.

How Much Information is Enough/Too Much

This last suggestion (going through back issues of the local paper) points out a happy fact.  Much of this information is ‘scientific guesswork’ – sure, the historical rain data is a matter of fact, but applying what happened last year, last decade, last century, to predict what will happen next week or month or year – there comes the guesswork.

So there’s only so much data you need.  There’s little point in spending lots of time and money to go from a 75% understanding of past rainfall to a 90% understanding, if you then go and make a guess with a huge +/- 100% factor in it anyway.

Averages, Maximums, Minimums

Now for the second part of the puzzle.  You’ve probably managed to find a chart of average monthly rainfall measurements, and you might have adjusted this a bit for any variations between the data you’ve found and the reality of your exact location.

But – here’s the problem.  To start off with an example, the average US family formerly used to consist of two adults and 2.5 children.  But have you ever seen a half child?  You can visit as many houses as you like, and while you’ll find many with two and many with three children, you’ll never find a house with half a child.

Another way of looking at an average is to say that an average is the number whereby half the time the reality is higher than this number, and the other half the time, the number is lower than this number.

What that means with rainfall numbers is that the monthly average rainfall will be, for half the time, higher than the actual rainfall.  Sometimes the actual rainfall might be a little less than the monthly average, and sometimes it might be a lot less.  This doesn’t matter to the statistician who has neatly calculated his 100 yr average number, but for you, it could mean the difference between having water and not having water – yes, the difference between life and death.

What you need to do is to establish a number a bit like flood plain numbers (you know, the 50 year and 100 year flood plain zones).  Do you want to base your needs on an average monthly rainfall figure that is half the time more positive than the actual rainfall will be in reality?  We suggest not.

But now comes the guesswork.  Do you want to use a monthly rainfall figure in your planning that is too high one year in three?  Or one year in five?  One year in ten?  How about one year in 50 or 100?

There is a cost associated with this, of course.  The more you want to plan for drier than normal years, the larger you’ll need to make your water storage capacity to carry you over from the good/wet months to the bad/dry months, and so the greater your cost will be.  Plus, sooner or later, you’ll end up with a number so huge that you’ll never be able to fill it based on the rainfall from the preceding wetter months (which circles us back, in such cases, to the need for a second water source).

You must look at a minimum of 10 years of data for each month you are studying.  If there is little variation from one year to the next, then you don’t have to build as big a safety margin into your figuring.  But if the numbers are all over the place, clearly you’re going to have to assume something close to the worst for planning your water needs.

But within what looks like a consistent set of data for perhaps 10 years can be other hidden longer term cycles – some weather cycles have a 60 or longer year period to go from minimum to maximum and back to minimum again.  Maybe the ten years you are looking at are the ten years at the best part of the cycle, which is now trending towards the worst part, which could show extremely different numbers.

At the very least, get an extended data series on an annual basis so you can see what overall variation there is, and if you’re looking at marginal weather and rainfall, you will need to be more careful about the data you are using.

Daily or Monthly or What Data

The longer the time period, the less variation in the numbers you’ll get.  If you look at annual rainfall totals, these will vary much less from year to year than if you look at each month’s data.  Whereas the chances are that your region’s annual rainfall is never zero, the chances may be that some months in some years, there’ll be an inch or more of rain, but in some months of other years, there might be not the slightest sprinkle for the entire 30 days.

The time period you need to drill down to depends to an extent on the size of the storage capacity you’ll be building.  The smaller the capacity, the more accurately you need to know when water will come in to replace the water going out.

Generally the monthly data is sufficient for most purposes.

However, daily data is useful for understanding how the rain falls during a month, so as to know whether to adjust the total rainfall to reflect light sprinkles that have little collectable net rain or not (see our section on Real World Imperfections in our earlier article on rainwater collection).

A Worked Example

Let’s have a look at some real world data for Seattle – not because we recommend that as a bug out location, of course, but just because there is readily obtainable information for the area.

First, let’s state our assumptions that we are using, above.  To be consistent with our earlier article on How Much Rainwater Can You Collect From Your Roof, let’s keep the same figure – 50 gallons of water a day or 1500 gallons a month for our basic household needs.  We also said that each inch of rain on our hypothetical roof will give us up to 763 gallons of collectible water.  So, by happy coincidence, it seems that as long as we are getting 2″ of water a month, we’re in good shape.

Can we be sure of getting at least 2″ of rain every month?  The first thing we do is look at the monthly average rainfall figures.  Let’s have a look at them on this page (other pages will have slightly different figures) :

 

Month Rainfall
January 5.5
February 4.2
March 3.7
April 2.5
May 1.7
June 1.5
July 0.8
August 1.1
September 1.9
October 3.5
November 5.9
December 5.9
Annual Total  38.1

 

Which brings us to the first important point.  If we looked just at the total rainfall for the year, we’d see 38.1″.  We need 24″, so upon seeing 38.1″, we might mistakenly think ‘Great, we have no problem’ and not look any further.

But look at the individual months.  You’ll see that the five month block from May through September all show less than 2″ of rain per month.  And if we look back at April, its 2.5″ figure looks a bit anxiety-causing too – remember this average is the number which will be too high half the time.  So with a need to have 2″ of rain in April, and no opportunity to top up with extra rain in May, we need to get an understanding for the possible variation of rain in April too.

Let’s now look carefully at the six months we’re worried about (April through September) and not only look at their monthly averages, but at the actual real rainfall that was measured in recent years.

We’ll take the information from this site.  The next table took a lot of time to type in, so please be appropriately respectful of the information presented to you!  And, just to show another thing, we are using their averages rather than those in the preceding table – quite a big difference in some cases, too.  (It seems this service changes their averages on a shorter sample of years than some of the other time bases).

We immediately noticed that regularly, the September rainfall was less than the 2″ we needed, so for those years, we looked at the October rainfall too, and with a shaky 2.17″ in 2008 for October, we looked at that year’s November.  The same thing happened in 2006, although massive rains in November helped the region catch up on its very dry summer.  Although the averages above suggested there’d be no problem in October, for one of the ten years in this sample there was.  If we don’t want to risk running out of water in October one year in ten, we need to look at that month too.

There’s more, with another deceptive average.  We also noticed that April couldn’t guarantee us 2″ of rain in three of the ten years either, so we added March data for years where that was necessary.  Fortunately, March rain was always above the 2″ we needed, so there was no need to look further back.

Month Avg  2011  2010  2009  2008  2007  2006  2005  2004  2003  2002 
March 3.75 3.65 4.42 2.18 2.13 6.49
April 2.59 4.47 3.49 3.36 1.90 0.69 2.73 3.68 0.65 2.74 4.29
May 1.78 3.20 2.83 3.61 0.89 1.46 1.65 3.32 2.53 1.16 1.11
June 1.49 1.42 2.49 0.18 1.64 1.34 1.67 1.63 0.81 0.51 1.73
July 0.79 0.71 0.31 0.06 0.48 1.44 0.06 1.03 0.16 0.06 0.64
August 0.88 0.13 0.64 1.16 2.87 0.73 0.02 0.29 3.00 0.32 0.04
September 1.50 1.29 4.80 1.75 0.78 3.16 1.43 0.95 2.80 0.89 0.42
October 3.48 3.45 5.54 2.17 1.55 3.01 8.95 0.66
November 6.57 6.52 15.63 3.71

 

Okay, hopefully your eyes aren’t glazing over from the over 80 data points in the above table.  Let’s first quickly skim through the data, month by month, and note the huge difference between wet years and dry years.  August went from 0.02″ all the way up to 3.00″.  October in 2002 had a mere 0.66″ of rain, but the next year, it had 8.95″.

Clearly the average monthly figures obscure massive swings from one year to the next.

Let’s now look at both the worst and the second worst rainfall figures for each month.  If we want to allow for a ‘one time in ten’ being wrong, we’d take the worst figure.  If we were prepared to consider a ‘one time in five years’ then we’d take the second worst figure.

Month Worst  Second
March 2.13 n/a
April 0.65 0.69
May 0.89 1.11
June 0.18 0.51
July 0.06 0.06
August 0.02 0.04
September 0.42 0.78
October 0.66 1.55
November 3.71 n/a

 

So we are now starting to make sort of progress, with an easy conclusion to draw and a difficult piece of further analysis.

The easy conclusion is that we can say we can reliably expect, on 1 April each year, to have full tanks due to having had more rain than we needed in March (and February and before).

We can also say that we can reliably expect, more or less on 1 November, that the rate of rainfall will start to increase above our offtake level.  We’d probably want to have a week or so remaining supply in case the November rains came late, but we know, for sure, that by the end of November, we’ll have received more rain than we consumed, and will end up the month with more water in our tanks than we started with.

Now for the really important part – the seven months of April through October.

If we wanted to be super conservative, we could simply take the lowest reading for each of these seven months and use that as the figure to work from.

But here’s an interesting thought.  Look at any of these months – let’s say August, for example.  In our table of lowest values, the lowest rainfall for August is 0.02″ (in 2006).  Now look at September.  Our lowest rainfall for September is 0.42″, in 2002.  Add these together, and you get 0.44″ for the two months.

But – and here’s the complicating factor.  In August 2006, we had the 0.02″, but in September 2006, we then had 1.43″ of rain – add these together and you get 1.45″ over two months.

If we look at the lowest September figure of 0.42″ in 2002, if we add the 2002 August figure of 0.04″ to that, we end up with 0.46″ – not very much more than the two lows, but still more.

So here’s the question.  We have one chance in ten that any given month’s figure is the lowest.  But what is the chance of the next month after that also being the lowest?  Does the weather in one month influence the weather the next month?  Sure, people talk about ‘dry summers’ or whatever, but is that a perception or a reality?

Let’s create another table, for the three most critical months (June, July, August).  We’ll compare the total of the lowest numbers from any year with the totals for each year.

Lowest  Second  2011  2010  2009  2008  2007  2006  2005  2004  2003  2002
0.26 0.61 2.26 3.44 1.40 4.99 3.51 1.75 2.95 3.97 0.89 2.41

 

So now we know that if we cherry pick the lowest months from each year, we can end up with the lowest total of 0.26″, and if we go to the second lowest, we are at 0.61″.  But if we insist that each month be linked to the month before and after, the lowest number now is 0.89″ and the next lowest number is 1.49″.

Confused yet?  So, what is your feeling – how much rain should we project to be sure of receiving in the three months of June, July and August?  We’re not going to answer that ourselves, because clearly there is no single right answer.

When you’ve answered that question to your own satisfaction, it is time for the key question :  How much rain do you think we’ll get for the entire period from 1 April through to sometime in early/mid November?

Clearly, there’s no exact or correct answer.  Depending on the level of risk you are prepared to accept for being wrong depends on the number you’ll choose.  If you guess wrong, then during the course of the dry months, you’ll realize the rain isn’t coming as it should, and you’ll see your water levels dropping below the levels you projected them to be, so you can start to adjust your water usage habits some.

That is relatively practical when you started off with a fair/generous projection of water usage to start with, and of course much harder if you were rather optimistic/aggressive about your water savings, giving you little room to cut back.

Further Interpretation of the Data

We’re going to look across the entire dry spell, from 1 April through to some time in November (let’s allow 500 gallons for November), and use our second worst numbers for each month.

But then we’re going to look at the individual months and see how the rain fell in those months and start adjusting for the less efficient collection of light sprinkles compared to the more efficient collection of downpours.

For example, in September’s 0.78″ result for 2008, we look at the relevant data and analyze the rainfall, day by day.

The first day with rain was the 20th, when temperatures ranged from 54 – 58, and the wind was 3.7 mph, and 0.54″ of rain fell.  We’ll say that 0.51″ of that was collected – after a long dry spell, albeit a damp day or two prior, there was probably a lot of moisture absorption and some evaporation off the roof going on.

On the next day another 0.02″ of rain fell, but the temperatures were warmer and the winds stronger, so we’re going to say none of that was collected.

On the 22nd, 0.01″ of rain fell, and that’s the minimum needed just to wet the roof, so we’ll ignore that.

On the 24th, we had 0.12″ of rain, and we’ll count 0.10″ as collectible.

On the 25th, temperatures were warm, the wind was strong, and 0.09″ of rain fell.  We’re going to say that only 0.045″ of that was collectible.

So add these adjusted figures together and round down, and instead of 0.78″, we have a net collection of 0.65″ of usable rain.

Let’s say after doing similar calculations for the other months, we end up with 3.8″ of rain in total that we can be sure will actually make it into our tanks.  This provides us with 2900 gallons of water.  But we are going to use 7 months of consumption at 1500 gallons a month, and we want 500 gallons left over on 1 November – a total requirement of 11,000 gallons.

So after adjusting for the rain that will come in , we need to start on 1 April with 8,100 gallons of water stored.  Now let’s adjust for evaporation – 0.25% a day, perhaps.  This means, for the seven month, 210 day period, we’ll lose 52.5% of our water.  We need to increase our storage from 8100 gallons up to say 12,500 gallons.

Can We Get the Rain We Need in the Wet Months to Fill Our Tanks

12,500 gallons is a lot of water.  It represents 16.4″ of rainfall.  Can we be sure of getting 16.4″ of rain during the wet months of November through March?

Yes, we probably can, even in a worst case scenario, but only just.  We’d simply repeat the analysis that we’ve already done for the dry season, and this time do it for the wet season to get a feeling for likely worst case scenarios.

In this case, our tanks will take the rest of the year to fill, and sometimes might not fill until early in the new year, giving only a few months of happily overflowing tanks and water-richness, before entering into another extended period of anxiously looking up at the sky each day.

The point to be aware of here, slightly obscured from using rainy Seattle’s data, is that the amount of rain we can collect in rainy months is sometimes insufficient for the drier months.  There’s no point in making the storage capacity any larger than the total amount of water likely to be collected off the roof.

Summary

So, we have learned both a general and a specific lesson from this example.  The specific lesson is how to work through a calculation for the water you’ll need based on your area’s rainfall patterns and your family’s water consumption.

The general lesson hasn’t yet been stated until now, but it needs to be considered.  Creating a water storage system capable of storing 12,500 gallons of water requires a sizeable amount of tankerage, and probably they will be at ground level so you’ll then need a water pump to transfer the water up to a holding tank in the ceiling for regular usage, so the water isn’t energy free.

Even a teensy-tiny well (2 gallons/hour capacity – barely a trickle) and perhaps a single 1500 gallon buffer/holding tank would give you the same results as your enormous 12,500 gallon rainwater collection system, and at massively lower cost.

These numbers were based on the climate in Seattle, an area renowned for its rain (albeit, as we’ve now seen in detail, somewhat unfairly).  Imagine how much worse it would be in a drier climate.  If we say 8 months with no water, that would call for 12,000 gallons, plus 500 for early November, and then if we say a higher 0.3% evaporation rate over 240 days, and you’d need to start off the dry season with 21,500 gallons of water stored.

There’s probably no way you could collect that much water during the shorter rainy season in this hypothetical alternate location, so like it or not, you’ll need a secondary water source right from the get-go in such cases.

One last point, if we may.  If you’re in a water scarce scenario, all other buildings on your property should also collect the water off their roofs too.  If you have a tool shed/workshop, an animal shed/barn, or whatever else, these could potentially double or more the rain you can collect.  And here’s the strange outcome of that.  If you are collecting twice as much rain, you don’t need as much storage.

May 152012
 

This map shows the variation between expected average rainfall (clear white) and actual rainfall for the first four months of 2012. 0% is dark brown, 200% is dark green. Clearly there's a huge divergence between average and actual rainfall.

We started off an earlier article about rainwater (see ‘An Overlooked Source of Water‘) by suggesting that a few 55 gallon drums of water taken from your downspouts would be a great source of emergency water in a Level 1 type, at-home, emergency.

If you’re planning for a short duration Level 1 situation, then you don’t need a lot of water, and even a single 55 gallon drum of rainwater would probably be enough – albeit on an uncomfortable hardship type basis – for a week or so, and larger quantities will allow you to enjoy successively more ‘creature comforts’ (such as flushing toilets).

But what about Level 2/3 situations – possibly a year or longer, when you need to be self-contained in everything you eat or drink?  A 55 gallon drum of water doesn’t go very far in that sort of case, does it!

Unless you’re in an area where it rains reliably every day, you’ll need to have some storage to give you water on the days when it doesn’t rain.  We talk about how much storage you might need in our article How Much Rain Water Can You/Should You Store.  This article concerns it more with appreciating how much water you can actually get from your roof collection system and matching it to your consumption level.

This and the other articles about rainwater storage might seem a bit complicated, and we deliberately go into quite a lot of detail.  But – what is more important than water in your life?  Sure, you don’t want to run out of food either, and shelter is important too, but if you don’t have a reliable supply of water, you’ve chosen the wrong place to shelter, and you’ll die of thirst long before you die of starvation.

Water is also a great comfort item.  Whether it be for enjoying a long soak in a tub of water, or singing in the shower, or just washing our clothing more regularly than arguably essential, a positive supply of water translates to a much improved quality of life.

So please do bear with us, and if you end up needing further advice or assistance, by all means contact us.

Water Consumption Rate

The first issue is the rate at which you will use water.  This is a very ‘elastic’ number, because in the worst case scenario, you can live on just a quart or two of water a day for some time.  But in a best case scenario, living a normal life such as most of us do at present, you’ll be going through as much as 100 or more gallons a day (true – look at your water bills the next few times you receive them and do the math yourself).

So somewhere between less than one and more than one hundred gallons of water a day is a number you can settle on as an appropriate compromise between cost and convenience.  Deciding on the exact number is outside the scope of this article – you need to decide what the number is, and then we’ll work forward from that.

For the sake of this example, let’s say you want 10 gallons of water for each of three people, and another 20 gallons of water for household things in general – 50 gallons a day for all of you, combined.

Agricultural Water

There’s another thing to consider as well.  While in a Level 2 situation you are basically surviving on your stored food supplies, in a Level 3 situation, you’re needing to grow your own food into the future.

And if you thought your personal and household needs for water were high, you ain’t seen nothing yet.  Here’s an interesting table of water requirements in terms of cubic meters of water per metric tonne of food yielded.

The numbers are very imprecise (even though they seem exact) because it is hard to know how much of the needed water can be supplied from the moisture in the ground to start with and how much needs to be added.  But just to seize some numbers off the site and convert them to US measures, you’re looking at almost 2,000 gallons of water per pound of steak you end up with after raising cattle, 700 gallons for a pound of pork meat, and ‘only’ 200 gallons per pound of wheat.

Our discussion that follows is primarily to do with domestic water for your residence.  But in choosing your retreat location, have an eye for what you’ll be growing there and what the water needs for that will be, too.

In most cases, it will be close to essential to have access to a free-flowing spring or a gravity fed water source to support your farming needs.  We can’t stress this too strongly.  Everything in an ongoing Level 3 situation revolves around convenient access to water.

Equating Consumption to Rainfall

You know – sort of – how many gallons of water you need per day.  But what does this translate to in terms of inches of rain?

The first thing you need to know is the collection area of your roof.  Don’t ask a roofer to do this for you, because he will probably tell you the number of ‘squares’ of tiles needed to lay your roof.  Because your roof is on an angle, the surface area of the roof is appreciably larger than the square feet of floor plan it covers.

So measure the exterior of your house, and add extra space for any roof extensions out over the sides of your house, and from these dimensions calculate the footprint on the ground of your roof.

You also should adjust for any areas of roof which don’t feed the rain into gutters.  Clearly if the water just runs off the side of the roof, it does you no good unless you add extra guttering.  If you have a separate garage and roof and plan to collect the water from that, include that in your calculation, too.

Let’s say you have 1400 sq ft of roof area, and the two sides which the roof slopes down to are each 40 ft long.  Maybe you have a couple of 5′ gaps where the water just runs off the side, but the other 70 ft in total are guttered.  So 70/80 * 1400 means you have 1225 net sq ft of collection area.

One inch of rain falling on 1000 sq ft of roof will deposit 623 gallons of water.  So each inch of rain on your roof will have 763 gallons of water going down your downspouts.

That is the theoretical best case outcome for this scenario.  We’ll fine tune it for the real world, but let’s first do a quick reality check before going any further.

In our example, you want 50 gallons of water a day, and you’ll collect 763 gallons of water from every inch of rain.  This means that in a year, you’ll consume 18,250 gallons of water, which will require 24 inches of rain (best case scenario).

Have a quick look at the average rainfall data for your region (see links below).  Just using the very basic annual rainfall average number, how much rainfall does your region get?  If the answer is less than 24″, you know that you’re either going to have to cut back on your water use, or you’re going to have to find additional sources of water.

Is Rainwater a Practical Partial or Complete Solution

Now for one further quick thought.  Maybe your region will give you 15″ or maybe even 30″ of water.  15″ is good – you could get 63% of your water needs from rainwater.  That’s great.  And obviously 30″ is brilliant.

But what say you can only expect 6″ of rain a year?  And what say none of that rain falls in June, July, August or September, and less than you’ll consume in May and October?  That means you’ll need to stockpile perhaps 7600 gallons of water in May to see you through to some time in October.  That’s a lot of storage, and a lot of cost.

Being as how you have already determined that you’ll need a well or some other water source, if you find a reasonable well (anything over a 2 gallon/hour well will be perfectly adequate – most wells will give you more than 2 gallons/minute!) is it really worth while also investing into a rainwater collection system?

Our recommendation would probably be to continue with your rainwater system, unless you were drawing water from a free-flowing spring or taking it via a gravity feed from a reliable clean year-round river.

There’s one interesting thing about rainwater.  It typically falls in months where solar and wind energy is the lowest – the winter months.  So maybe you use a solar/wind powered pump to draw up water from a well in the summer months, when you have plenty of energy but not much rainwater, and in the winter months, you use rainwater at a time when you have plenty of rain but not much energy.  The two sources balance each other out nicely.

In a Level 3 situation, you’ll be on your own for the foreseeable future with only the resources you have at hand.  Energy will be terribly scarce, as will spare parts for water pumps, and anything you can do to use as much low tech/energy free resources to  help extend the useful life you can get from energy powered and higher tech solutions is to be considered as compelling.  After all, once your high-tech gadgets are gone, they’re probably gone for good.

Furthermore, you know you can trust the water you collect from your roof. Well water is probably okay, as long as you know what else is happening to the water table, but river water depends on what is upstream of you – something you mightn’t be able to control.  That herd of deer that likes to go down to the river to drink?  Guess what else they do at the same time?  The camp set up by the less well prepared survivors of the city a mile up-river?  What do you think they do to their sewage?  Yup – you’re drinking it.

For all reasons, we urge you to keep a month or more’s emergency supply of water on hand – what say your well’s pump breaks, or the river dries up or ices over for the first time in 50 years?

So if you have some tankerage already in place for a reserve supply of water, why not use it to collect the rainwater you get as a supplementary source of water whenever possible, to save on your water pump and the energy needed to drive it.

Real World Imperfections in Water Collection

Remember back to our theoretical collection of 623 gallons of water for every 1000 sq ft of collection area (ie roof)?  Well, now let’s start considering some of the imperfections that reduced the true net water you actually get in your tank from the rain that falls on your roof.

What say you have a very light drizzle on a warm windy day?  What say your roof is made of wood shakes?  Maybe the first bit of rain will soak into the wood, and maybe the warm wind will evaporate most of the light drizzle before it forms into sufficiently large droplets on the roof to start tumbling down and into the gutters.

Maybe you have some dirt, leaves, moss, or debris of any other sort on your roof (and in your gutters) that soaks up some of the water too.

Whatever the circumstance, it should be obvious that a very light drizzle, while possibly adding up to a measurable amount of rain over some hours, might actually be entirely uncollectable.

The steeper the pitch of your roof, the less rain you need to get the water started running down and into the gutters.  If you have a smooth impervious substance like tile or metal, the water will run more readily than if you have a textured or slightly absorbent material such as artificial or natural wood shakes.

For months when the amount of rain that falls is probably less than the minimum you need, these issues become relevant.  You need to analyze how the rain falls, on a daily basis (or even hourly but this is probably not readily available) to determine how much of the rain will end up being collected and how much will be lost.

Our own experimenting has suggested that the first 0.01″ (one hundredth of an inch) of rain is lost, and if the rain is falling very slowly, there will be appreciable ongoing losses.  A 1″ downpour, all within an hour, will give you close to 100% water recovery, but a fine drizzle totaling 1″ over two days might see you only collect half the water (this is a WAG on our part!).

Storage Losses

You know that water boils at 212°, and if you think about it for a moment, you also know that water evaporates, without boiling, at lower temperatures too.  Even a lump of ice loses some of its mass each day due to evaporation.

How much water will you lose out of your tanks due to evaporative losses?  This depends on the ratio of the surface area of the tank to the volume of water within it, the amount of open space above the water, the temperature of the water and of the air (the two might be very different), the ambient humidity, and if there are any winds blowing over the surface of the water.  It even depends on the altitude you are at.

That is enough variables to make it very difficult to offer up for sure always accurate rules of thumb for calculating evaporative water losses.  Suffice it to say that the cooler you keep your water, and the more enclosed you can keep the top of it, and the smaller the surface area as a proportion to water stored, the lower your water losses.  You can’t really control the outside temperature or humidity, but you can stop winds from blowing over your water (and over any openings) and you can perhaps insulate the tank some and maybe even bury some or all of it to take advantage of the natural tendency of the ground to be cooler in summer (and warmer in winter, too – you don’t want your water and pipes freezing up come winter-time).

If you’d like to see an excellent worked through formula, you can go to this webpage which concludes that a typical cup of water would take 44 days to evaporate in a still room at 72°.  In other words, it is sort of evaporating at a rate of 2.3% a day, at least for the first day.

Let’s use the same formula and basic data, but instead say we had the cup of water outside at 85°, and the humidity was 40% rather than 60%, and there was perhaps a light 3 mph breeze running across the top of the water.  This would give us a massively different result – the water would be gone in 11 1/4 days!  You’re losing almost 10% of the water every day.

Clearly, the rate of evaporative loss can be a huge factor and has to be carefully optimized.  Let’s say you can limit your evaporative losses to 1% a day with careful design.  But this does mean that if you need 1000 gallons at the end of 30 days, you’ll need to start off with 1300 gallons at the beginning of the month.  That’s a significant impact.  And if you’re storing 10,000 gallons to last you six months, if you’re experiencing even ‘only’ a 0.5% loss a day, that comes to 9,000 gallons.  Yup – you’ll lose 9,000 of your 10,000 gallons just to evaporation.

Okay, we are slightly simplifying things here, but you see the issue.  The most important thing to obsess over in designing your water storage system is the evaporative loss of your stored water.

Water Collection Rate

So you need (in the case of our worked example) 50 gallons of water a day, right.  Let’s run the risk of stating the obvious, and make two assumptions.

First, if you are getting more than 50 gallons coming down your downspouts each day, you’re free of problems.

Second, it doesn’t rain every day.  Even if you average 50 gallons a day of water collected, you’ll probably be getting less in the summer and more in the winter, and you’ll have occasional unseasonably dry spells that you’ll need to plan for.  Sure, you might get some unseasonably wet spells too, but they are not so relevant.

You need a buffer of stored water to carry you over the dry days with no rain or insufficient rain.  How big a buffer should that be?

It all depends on the rainfall pattern in your local area.  You’ll need to go off and do some research to get not just monthly average rainfall numbers, but hopefully daily rainfall data and averages for many years.

How do you do this?  Well, we’re glad you asked that question!  Please now visit our article How Much Rainwater Can You/Should You Store for a detailed working through of how this can be analyzed and calculated.

May 142012
 

A simple but impressive rainwater collection system.

A person can survive on much less than a gallon of water a day in an emergency (the actual amount depends on things like the type of food you might be eating, the work you are doing, the temperature and humidity of your environment, and your height, weight and age).

But a common rule of thumb is that in an adverse situation, you should plan on about 1 gallon of water, per person, per day.  This keeps you from being dehydrated, and gives you extra water to cook in, and even some to brush your teeth with, too.

But you don’t get any to flush with.  Even modern low flow toilets use 1.6 gallons every time you flush.

The real-world amount of water we actually use in our comfortable lives every day is much greater than the essential need for several pints to keep dehydration at bay.  In addition to toilet flushing, there is dish washing, clothes washing, showers and baths, car washing, garden watering, and who knows what else.  Estimates vary enormously, and there are doubtless regional variations, but it seems the average American uses between 50 – 100 gallons of fresh water every day.

In a Level 1 event, you are going to want to ‘hunker down’ at home for as much as a week (much more than that and you’re moving into Level 2 territory).  The chances are high that you’ll have water, the same as always.  But that is far from guaranteed.  Maybe you have experienced an earthquake that has broken the water mains, for example.  Or a major power outage that means no electricity to drive the water pumps that send the water to your faucets.

Part of the hope in a Level 1 event is that you can continue to live a reasonably normal life during the short-term nature of the event, and due to the event’s anticipated short-term, you choose to stock enough essentials to ensure as much of your comfort as you wish.

So what should you do about water?  And, if you’re going to store some, how should you do so?

It seems to be prudent to keep at least enough water to allow for the essential ingredients of life to continue – maybe a gallon per person per day for essential uses, and some more for not quite so essential uses such as toilet flushing and at least sponge baths.  (Do we need to remind you of the old saying ‘If its yellow, let it mellow; if its brown, flush it down’?)

So maybe you decide you want to have 10 gallons, per person, per day, and maybe you want to be sure to have a ten day supply for three people.  That’s quite a lot of water – 300 gallons.  To look at it another way, that’s over a ton of water, and with the weight of the containers that hold it, you’re probably up to a ton and a half.  (Water weighs 8.35lb per US gallon.)

One more perspective on this 300 gallon supply.  If you’ve been saving up 2 liter drink bottles to keep water in, you’ll need 568 bottles to hold 300 gallons (there are 3.785 liters in a US gallon of water).

Well, don’t let us stop you from buying plenty of 2 liter bottles of Coke, and some industrial grade shelving to stack and stock your water supplies on.  But there’s one source of water, and one easy way of storing it, that most people overlook.

Rainwater

If you live in a dwelling with a roof (ie not in an apartment complex) your house or condo’s roof can be a great rainwater collector.  Best of all, most of what you need is already there; you don’t need to make many modifications at all to be able to get the rain from the roof and into storage.

To encourage you some more, here’s an interesting statistic.  For every 1,000 sq ft of roof area, your roof will collect 623 gallons of water from each inch of rainfall.  Or, to put it another way, with three people each wishing for 10 gallons of water a day, you need a daily average of only 1/20th of an inch of rain.  Well, actually, that wouldn’t work, because 1/20th of an inch of rain would just wet the roof rather than run off it to be collected, but you get the point, I’m sure.

Better to say that if you had 1/2 an inch of rain fall once every ten days, each 300 sq ft of roof would supply enough water for one person.

Okay, point taken.  If you live somewhere wet (like Seattle!) then here’s one of the good sides to this – even the driest month of July still sees 0.79″ of rain, and apart from August at 0.97″, all the other months are way over an inch of rainfall.  But you probably know that, ‘unscientifically’, just from living here, don’t you!

How to Collect Rainwater

This is dead simple.  Although you can do more complicated things, all you need to do is put a rainwater barrel in your downspouts.  There are a couple of things you can do to make this more useful, however.

The first thing is that you want to have your barrels up as high as possible, so you can gravity feed the water on from the barrel to where you’ll be using it, and the more the height differential, the more the pressure from the water in the barrel down to wherever the water eventually comes out of a tap.

From the point of view of the rain coming off the roof, it makes no difference at all if the barrel is immediately under the eaves, or sunk into the ground.

Don’t put the barrel ridiculously high up, though, because you’re going to need some way to get water out of the barrel as and when needed.  The simplest consideration involves two things.  First, you want to be able to reach a tap on the bottom of the barrel.  Second, you want to be able to run a hose from the tap, through a window, and into your house, with hopefully the hose able to run downhill all the way, even if only on a gentle slope.

You also don’t want to get too carried away with scaffolding to support barrels way up the side of your house, and maybe some of the people in your family won’t think they’re the most appealing of ornaments either.

So work out whatever you can as best you can.  Chances are you have several downspouts around the perimeter of your house, you’ll want to do this at as many of them as you feel motivated to tackle.

This water is also great for the garden too, and if you have a fair amount of collection capacity, it might be useful to use it for gardening, in dry months, especially if your local water authority adds any sort of restrictions or surcharges on ‘excessive’ water use.

Water Barrels

You can collect water in anything you like that is reasonably big, which doesn’t leak too much, and which doesn’t add nasty flavors or chemicals to the water.

Most people will choose plastic food grade type barrels.  These can be purchased new (of course) and sometimes used – they are recycled barrels that held some sort of food product or chemical, and which the supplier may or may not promise to have fully cleaned, although often you’ll see that in one point they talk about ‘triple cleaning’ the barrels, and at another point, they also recommend against using them for storing drinking water.

For non-drinking water purposes, used barrels are fine.  But for drinking water, and unless you want to have to either accept some strange flavors or treat/purify the water, it is probably best to get brand new barrels.

Some people will quite rightly avoid plastic entirely, and have the budget to spring for stainless steel.  Others might use galvanized iron, or even wood (probably not a good idea – don’t let wood dry out too much or else it will shrink and the barrel becomes less water-tight).  Fiberglass works.  Glass is great, but sadly impractical.  You can even make water barrels (more like tanks, really) from concrete if you’re wanting something huge in size.

Whatever type of container you get, it is wise to thoroughly rinse and sanitize it (them) before putting water in them.

Choose an opaque color.  Sunlight is as bad for water storage as it is for anything/everything else, so try and keep the water dark (and ideally cool, too, but that might be asking for a bit much).

As for the size of the barrel, there’s no right or wrong answer to that.  Well, clearly there are upper and lower limits – below a certain size and it isn’t worth the bother, and above a certain size and you’ll never fill it.  If you’re looking at typical sized 30 – 55 gallon drum, you will probably end up with close on your target 300 gallons of water, all stored ‘automatically’ for you outside.

A 55 gallon plastic drum, full of water, will probably weigh about 470 lbs – plus the weight of the structure it is mounted on, of course. A 30 gallon drum would be more like 260 lbs.  Both are way too heavy to ever carry, but the 30 gal drum has the benefit of not needing quite as strong a support structure.

Plastic water barrels will cost you anywhere from less than 50c to more than $2 per gallon of storage capacity, depending on the type, their fittings, and where you source them from.

Multiple Barrels Per Downspout

If you wanted to, you could also put multiple barrels, side by side, at each collection point.  Simply run a pipe between the bottom/lower side of one barrel to the same place on the other barrel.  The two barrels will fill evenly and subsequently empty evenly, too.

Alternatively, you could stack one above the other.  If the bottom barrel can be sealed, you simply run a pipe from the bottom of the top barrel to the top of the second barrel, and you take your water out of the double barrel from a pipe at the bottom of the lower barrel.

If the second barrel is not watertight, you’d want the connector to go from the overflow point on the top barrel down to anywhere on the bottom barrel, and you’d then need two points to take the water out from – the bottom of the top barrel and the bottom of the second barrel.  Maybe the lower barrel is below the window or whatever, and you designate this as your ’emergency spare’ and also for garden water, whereas the top barrel with the more convenient water flow is for your main indoor needs.

Connecting Your Barrel to Your Downspouting

This is easy.  Cut and divert your downspouting so that the water pours into the top of your barrel.  Arrange a generous sized overflow tube, also at the top of the barrel to allow overflow water, after the barrel is full, to then go back into the rest of your downspouting.

Be careful that the water coming into the barrel doesn’t just go straight into the overflow exit pipe.

At the bottom of the barrel, you’ll want to fit (or have fitted for you) a regular outdoor tap with a thread for regular hose, so you can then take the water from the barrel, probably via a regular hose, and into the house (or wherever else you want to use it).

Modify as needed if you are having two or more barrels linked together.

Linking Your Barrels Together

This is a great idea.  Maybe you have four downspouts, and a barrel at each one.  Rather than have four hoses all leading into your house, you could instead link the four barrels together and just have one hose, from whichever is the most convenient barrel, to feed into your house.

Simply run a hose from the bottom of each barrel to the bottom of each other barrel.  The hose can even go down to ground level before going up again to the next barrel, it doesn’t really matter, because the rate of water flow through these balancing/transfer hoses can be reasonably low.

For this to work it is important that the barrels be at close to the same height off the ground.  You are making use of the magical property of water to settle at the same level, even if in multiple barrels in multiple locations.  You can easily test the relative heights just by filling all the barrels with about an inch or two of water (so they don’t get too heavy).  You should see the same amount of water in each barrel.  If one has more water in it than the others, you need to raise it however many inches to balance it to the others.

Is Rainwater from the Roof Safe to Drink

Many people enjoy long and healthy lives drinking untreated rainwater from their roofs.

Indeed, when the writer was a child, he lived for some years in a town where his parent’s house relied exclusively on rainwater.  The roof was made from painted corrugated iron, and the water tanks were of galvanized iron.  He remembers as a little boy playing with the tanks, and never thinking to question the dirt in the gutters that the rainwater passed through, or all the slime and sludge in the bottom of the tanks.

Birds would fly overhead and do what they do, and who knows what else happened to the water as well.  It was not treated in any way; it just went straight from the roof to the holding tanks, and from them to the taps inside (this was well before people started drinking bottled water – 100% of all our water came from the tanks).

There are some common sense issues to consider, however.  Try and keep your water away from zinc (such as sometimes used to reduce moss growth), from lead (in paint or flashings), and from treated timbers.  Any sort of new roof should be treated warily before it has had plenty of rain rinse it off.  You don’t want any overflow or discharge pipes from hot water tanks or a/c units to drain onto the roof and potentially into your water tanks.

Screening the tanks can help prevent large (and small) insects and animals get into your tanks.

If you’re in a polluted area, you have a bit more reason to be validly concerned.  All that pollution up in the air slowly settles down, and some of it lands on your roof.  Rain then washes it into your water tanks.

One rule of thumb is that if the water looks clean, smells clean and tastes clean, it is probably fine to drink, especially for a limited period of time.  But if you are concerned about pollution being washed into the water, or just don’t like the thought of drinking water from your dirty roof, by all means filter and treat the water before drinking it.  Or use your outdoor water for non-drinking purposes (cleaning and toilet flushing) and supplement it with the gallon per day of water you feel to be better for drinking purposes.

One plus about rainwater.  Depending on how you might choose to treat/purify it (sometime it would be great to understand how adding chemicals to water is considered to be purification!), you’ll be getting water with no fluoride added to it, no chlorine, and no other nasty chemicals that may or may not have harmful side effects.

Rainwater is generally ‘soft’ rather than ‘hard’.

How Much Water Should You Store

This very essential aspect to do with planning a rainwater system deserves its own page.  And so it now has one – please see How to Calculate How Much Rainwater You Should Store for a mind-numbingly thorough discussion on this point.

 How Long Can You Store Water?

This might seem like a strange question.  Water is just water, right?  H2O.  What can go ‘stale’ with water?

Well, yes, in a perfect world, that is true.  But inevitably, you get biological contamination, and also some other contamination that might become food for the biological contamination.  Add some sun and some nice warm conditions, and even clean pure water will eventually end up with algae and other types of biological contamination.

As the water falls through the air, it picks up contaminants.  It picks up more as it runs over the roof and into your storage.  So rainwater can be somewhat biologically active to start with.

Furthermore, there is always the danger of chemicals leaching out of plastic storage containers and into the water.  This happens slowly over time, so the longer water stays in the same plastic container (and the warmer the temperature and the more the sun) the more leaching will occur.  Smaller containers have a greater surface area to volume ratio, and so need to be emptied and refilled more frequently than larger containers.

Some people recommend changing any stored water once a year.  Others say they’ve had no problems with ‘old’ water many years old.

For ourselves, the nice thing about rainwater is that (depending on your rainfall, storage capacity, and usage patterns) you’re probably turning over the water in your tanks more than once a year anyway.  We definitely renew the plastic bottled water we have indoors every year or so, but the outside water, as long as it is being sort of renewed – either just by surplus rainwater overflowing out of the barrels, or from garden watering and refilling – we don’t worry about, especially if it is water that isn’t our prime drinking water to start with.

Maintaining the Barrels

There’s not a lot that you need to do to maintain the barrels.  Check for leaks, especially around the taps.  Maybe once every five or so years, if you see visible accumulations of algae and sludge in the barrels, clean them out.

An easy way of cleaning the barrels is to use a siphon and just move the end of the siphon tube that is in the tank around to suck up the stuff from the bottom of the barrel.  You won’t need to completely empty the barrel that way.

Needless to say, such activities are best done at a time when rain is forecast in the foreseeable future so as to be able to replenish your water stocks (but there’s no need to do it in the middle of the downpour!).

Legal Issues

Alas, in some jurisdictions, the water that falls on your roof of your house, on your property, may not belong to you!  Anxious environmentalists may be concerned that you are diverting the water from its ‘normal’ path to wherever it would otherwise go (let’s ignore than a house and roof creates an un-normal water collecting/concentrating point to start with, shall we….).

In other states with water shortages and complex water rights, it has been argued that by collecting the rainwater, you are stopping it from mysteriously migrating on to the state’s water supply, and therefore, you are depriving the owners of the water rights of their water (this is definitely the case in Colorado).

The simple act of building structures to hold water barrels may require building permits too.

Summary

Adding a water collection facility to your roof’s downspouting can be an easy project you can do yourself, and will provide you with a store of extra water, either for personal use in a Level 1 emergency, or simply to water your garden with and place less stress on the town water system.

There is one difficult paradox – the months when you most need water are the months when it rains the least.  This means that you’ll need to have somewhat larger storage capacity (from the wet months) to carry you through the dry months.

May 072012
 

Two cans, side by side, of the same product in the store, one with more than twice the shelf life of the other

Nothing lasts forever – least of all, alas, ourselves.  But, if we can ignore that most relevant of all issues (at least for now), let’s instead look at how long any food item will last, and how can we give it maximum longevity.

In a very simplified form, the life of any food item varies depending on a number of different factors.  Some types of food are more sensitive to some storage issues, others are less sensitive, and of course, some types of food start off with only short shelf lives and little chance of extending them, whereas other food items are inherently long-lived and can be extended considerably further.

It seems that the current ‘state of the art’ for extended shelf life products is expressed in the commonly found freeze-dried foods that offer the promise of a 25 year shelf life.  Is this realistic?  Ask us in twenty-something years!

Not to get ahead of the article, but even a tin of freeze-dried product with a 25 year shelf life claim can have a longer or shorter life depending on a number of facts as to how it is stored.  Of course, the tin of product has been designed to control many of those factors just by nature of it being a sealed tin, but others still apply.

So let’s consider the major factors as they relate to any and all food products and the shelf life you can expect from them :

  • Bio-activity (ie fresh fruit or meat going ‘rotten’, seed germinating, etc)
  • Water/moisture – (Both humidity and liquid water can trigger or accelerate bio-activity)
  • Oxygen (and sometimes other gases too)
  • Light (although some things may be activated also by the lack of light)
  • External contamination/pests/etc
  • Temperature (usually the cooler the better)

The one reliable constant factor that can be said in all cases is that the warmer the temperature an item is stored at, the more rapidly it will spoil, whereas the cooler the temperature, the longer it will last.

Having said that, there are practical limits to how cold you should chill items down to.  Sometimes it is not a good thing to freeze items – the freezing of the moisture inside the item may break up the item’s cells, making it go mushy when unfrozen.  But in most cases, keeping an item down around 40° or thereabouts will appreciably extend the life of the item in question.

How to Tell if Food is Still Good or Bad?

The words ‘good’ and ‘bad’ need quote marks around them in the heading, because they are subjective measures rather than absolute measures.  And they can have several different meanings.

One measure of bad food is when an item has become unhealthy to eat – when it has acquired a significant level of harmful bacteria or toxins such as to make a person eating the food item unwell.  Even this is not an absolute measure, because some people have stronger stomachs than others.

Another measure is when a food item no longer looks attractive or smells appealing.  These of course are subjective measures too, and it is fair to say that what looks unappealing to a person in middle class suburban comfort today might look extremely appealing to a starving person post TEOTWAWKI tomorrow.

Our sense of ‘bad’ food is a fairly reliable predictor of safe/unsafe food.  If food looks and smells bad, and if you proceed to taste it and it tastes bad too, it probably is bad.

Yet another measure is when the nutritional value of the food item has reduced down to something close to zero.  This is impossible to detect by looking/smelling/tasting; but you’ll find out empirically.  If after eating a food item for several days, your weight goes down and health deteriorates, probably the food has lost most of its nutritional value.

MREs as an Interesting Example of Time vs Temperature

Just exactly how much extra storage life can you expect by keeping your stores cooler than you otherwise would?  There’s no exact answer to that question, but a couple of elaborate tests of MREs give us some clues.

Testing of the MRE formulation in the 1980s (which included free-dried food items) by the Army’s Natick laboratory were conducted, using a panel of ‘average’ people, and having them do subjective taste testing, with the results then averaged to try and create some consistent measures.

These taste tests showed that the shelf life of MREs ranged from as short as one month if the MREs were stored at 120° to as long as 130 months if the MREs were stored at 60°.

The report said that longer shelf life would be possible at temperatures below 60°, but the test did not have the time to study this.  It also said that food which was rejected by the panelists as unappealing was still nutritious and healthy, even though it no longer looked, smelled or tasted appealing.

Here’s a table showing the results.

Temperature
(°F)
Storage Life
(Months)
months increase
(from previous row)
% increase
(from previous row)
120 1 n/a n/a
110 5 4 400%
100 22 17 340%
90 55 33 150%
80 76 21 40%
70 100 24 30%
60 130 30 30%

 

The key learning point here is not so much the increase in shelf life between 120° and 110°, but more relevantly, the increase in shelf life between 70° (the temperature are houses are at, most of the time) and 60°.

The implication of this is that we can increase the shelf life of many products that we store by a sizeable amount – 30%, which in many cases will mean another year or more of shelf life – by doing nothing more complicated than keeping them in the coolest part of the house.  That closet in your basement, rather than upstairs in the sunny pantry.

After the reformulation of MREs, a new set of tests was run.  The results aren’t directly mappable to the other set of results, and show the new MREs have much shorter shelf lives.  Here’s the best guess we can make on the new results to show them in similar format to the old ones

Temperature
(°F)
Storage Life
(Months)
months increase
(from previous row)
% increase
(from previous row)
120 1 n/a n/a
110 2.5 1.5 150%
100 6 3.5 140%
90 18 12 200%
80 36 18 100%
70 40 4 10%
60 48 8 20%
50 60 12 25%

 

These results are interesting because they add another data point – the additional extension in shelf life at 50° rather than at 60°.

The earlier set of results showed a 30% shelf life extension by going from 70° down to 60°; this newer set shows a lower 20% extension, with a further 25% extension if dropping the temperature by another 10°.  While not quite as drastic as the earlier set of results, 20% is still better than nothing, and probably for no more effort than moving your stores from one part of your house to another, and in the possible event that this cool area averages closer to 50° than 60°, you’re getting as much as 45% extra life compared to leaving them in the warmer part of your house.

Here’s a good page with some interesting pictures of applesauce and cheese spread (click them to see more) that has been stored at different temperatures and times.

Why the Variation in Shelf Life Extensions?

You’ll see there is no constant variation in shelf life extensions per ten degrees of temperature change – either in terms of months or percentages.  This is slightly puzzling because most chemical reactions speed up at a constant rate related to temperature increases, and so we would normally expect to see steady percentage changes.

There are two factors at issue here for why some ten degree steps have larger or smaller impacts on shelf life than others.

The first is sampling and testing errors.  There is no scientific exact way of rating food as good or bad based on appearance and taste, so the personal preferences of the samplers will add an element of randomness to the numbers.  We’d suggest all numbers be viewed as plus or minus 10% of reality, which enables us to say, for example in the second set of results ‘10% plus a 10% sampling error is within the same zone as 25% less a 10% sampling error’.

The second is that different processes are triggered at different temperature points.  Some processes might be dormant at all temperatures below a certain number, but ‘wake up’ and start impacting on shelf life above a certain point.

What Does the Shelf Life Statement on a Food Item Mean?

So there you are, looking at your can of baked beans, and studying the ‘Best By’ date printed on it.  How was that determined, and what happens the day after this date?

The USDA has a page that explains some of the distinctions between ‘Use By’, ‘Sell By’, and ‘Best By’ dates.  Some of what they say is vague and meaningless, and the key take-away point is that these dates for non-perishable food items (ie not raw meat, fruit, etc) are not very exact or scientific.

We suspect – but absolutely don’t know for sure – that some food manufacturers find themselves steering a compromise path between setting dates that are too ridiculously short (which might discourage people from buying their products) and dates which are extended well into the future (which would reduce the amount of food people either junk or eat in a rush due to it being about to expire, and which also could create liability if the food is not well stored).

The significance of the date you see is not actually the date itself, but how far into the future it is.  If we say that, to be on the safe side, manufacturers assume a storage temperature of 80°, and you actually store the item at 50°, then this could be enough to give you an extra 65% of storage life.  So if the date shows you have two years remaining when you buy the item, maybe that means you really have, in your cooler store, an equivalent of just over three years.

Plus also remember that these dates are when the food first starts to become less than prime/perfect.  There’s an unknown amount of extra time into the future before it becomes appreciably less than appealing.

Pure Seed and Grain Storage – More Temperature Dependent

Here is an excellent page of information about storing grains and seeds, including rice and wheat.  It cites the USDA in claiming that a 10.1°F change in temperature will halve or double the shelf life of the product being stored (depending on if the temperature goes up or down).

The two main points from this page are to keep items cool and oxygen free, and that whole wheat keeps a lot longer than flour, and white rice much longer than brown – you probably already knew these things, and now you’ll understand why, too.

These rates of change are much greater than observed with the MREs.  We guess this may be because the MREs have been treated to give them some longevity so the usual ‘laws’ of biological activity and their dependence on temperature have been modified.

Special Case :  Medicines

Very good news here.  The expiry dates on medicines are ridiculously conservative.  With the exception of insulin, liquid suspension antibiotics and nitroglycerin, most medications can be considered to remain active and potent for ten years beyond their expiration dates.

Again, the same as other items, the cooler you keep them, the longer they’ll last.

Useful Tip :  Check Shelf Life in the Store Before Buying

You probably know, when buying milk or other products with a short shelf life, it pays to check the expiry date before selecting the product in the store.  Sometimes you’ll note a carton several back from the one in front might have a week or more of extra shelf life – ie, the milk cartons in front offer one week, and the ones behind them offer two weeks.  If you’re not sure how long the carton of milk will last you, it for sure makes sense to take one from the back of the line.

Surprisingly, this is true of other items too.  We were in a local supermarket today and observed cans of tomatoes on sale.  Tomatoes – an acidic product – typically have a shorter shelf life.  Some of the cans were showing an expiry of March 2013 (ie 10 months from now) but some of them were showing an expiry of March 2014 (ie 22 months from now – more than twice as long).

And if we were to store them in a cool place, getting perhaps a 50% extension in shelf life as a result, that would get us an extra 18 months of storage time on the longer dated product.

This was an astonishing difference in shelf life statements.  So if you’re buying even canned goods that you won’t be immediately opening and eating, be sure to check the shelf life statements on the cans, and choose your cans accordingly.

Summary

Shelf life statements on food items you purchase are not exact magical dates whereby the food is perfect up until midnight on that date, and then useless/dangerous from that point forwards.  If anything, these dates represent the shortest amount of life you can expect from food items, not the longest.

Shelf life of all items is massively influenced by temperature.  A change of 10° may as much as double (or halve) the shelf life of food items; there will be less impact on pre-processed items, more impact on unprocessed items.

Always keep everything as cool as possible, but most products should be kept slightly above freezing point.