Slice of Heaven in a Can (SOHIAC) is my project to develop an inexpensive, minimalist solution to the issue of homelessness due to disaster or societal conditions, by reusing surplus ISO shipping containers as a basic construction module.  

Access to a clean, safe water supply is one of the most fundamental issues to solve in providing basic housing anywhere. A person in good health can live 30 - 60 days without food, but only about 3 days without water. Natural disasters and war are disruptive to water supplies. According to research figures about one fifth of the world’s population does not have access to clean, safe water. Fully one third of the planet is considered “water stressed,” in which the water supply is precarious. And even in the US, water can be a determining factor in deciding whether a location is “livable” or not. Even where water supply systems exist, the cost of attaching to the grid is a significant expense.

One underused resource in the US is rainwater catchment. In our cities rainwater is primarily a waste disposal issue, with costly storm drain systems having to be built to carry it away. But in some rural areas, such as in Texas and Hawai’i, there is a long tradition of catching rainwater for domestic and agricultural purposes.

Catching rain is easy to do with just a little thought. In the illustration above I show components of a minimal system: a sloping roof, a rain gutter, a downspout, and a catchment container. Tile or metal roofs are best for the purpose, and a shallow slope of 2 in 12 rise is optimum, but even a tarp or a steeper roof is usable. The formula for the harvest capacity is .6 gallons per inch of rain per square foot, calculated on the footprint of the catchment surface, not the surface area. So in the example given, with 160 sq ft of collection, 1 inch of rain will theoretically yield 96 gallons, or nearly 2 of those 55 gallon drums pictured.  

In practice, the efficiency of collection is lower due to splashing, gutter overflow, etc. Also it is standard practice to let the first portion run off before starting collection, to flush off surface dirt and debris, so planning for 70 - 80% effective yield is wise. Worldwide the average annual rainfall is 32” per year, which would yield over 2,000 gallons a year in this example. In my target area for the pilot project in Hawai’i, the average rainfall is 100” per year, or nearly 7,000 gallons a year harvest from this one small roof.

Storing water is a topic in itself, which I will cover later. In an emergency situation the water captured could be used raw for survival, but it carries certain health risks, including trapped particulate matter, dissolved atmospheric gasses, bird and animal droppings, and other contaminants. The accepted practice for high dollar installations is to pump the rainwater through course and fine filters, and then sterilize the water with ultraviolet light or ozone generation. These options are simply too costly to purchase and install to be practical in this usage.

Fortunately there is now a very low cost, very simple alternative available which can turn any kind of water, even ditch water, into safe, potable water. For $18.50, the .5 micron ceramic dome filter pictured below, packed with activated charcoal and other absorbents, will provide safe water for a whole household for 6 – 8 months. And with two same-sized containers… 5 gallon buckets, trash cans, clean barrels, whatever… and a spigot you have a complete system for purifying the rainwater. Used simply as a drip filter, it will purify a gallon an hour. Under pressure, it can handle up to 300 gallons per hour.

It is effective enough to remove fecal contamination and other disease causing bacterial contamination from ditch water. And the only maintenance required during its effective life is to scrub off the ceramic surface every two weeks with a toothbrush or damp cloth. Even for urban households, this could be a very useful item to have on hand as part of disaster planning supplies. Shelflife of the unopened package is 3 years or more.

Ceramic dome filter (with pre-filter sock), two 5 gallon buckets, spigot - a complete water filtration system for ~ $30 

Here are tsunami survivors in India with assembled life-sustaining water filtration units

This girl in Paraguay is drawing safe, clean drinking water from a larger drip filtration unit made from clean garbage cans. Same filter. 

I have no connection with the folks who make and sell this remarkable filter, which can be purchased through the link at the bottom, but I’m impressed that they have made them available for purchase at such a low price. And they have set up a way for you to purchase them and contribute them directly to the Haiti recovery effort if you wish. Good people. Their specs for the filter follow:

Product is manufactured to meet:

National Sanitation Foundation (NSF) Standard 42
National Sanitation Foundation (NSF) Standard 53
iso 9002 Quality Standard
usa ael Laboratories
usa Analytical Food Laboratories
usa Johns Hopkins University
British 5750 Quality Standard
England’s Water Research council (WRc) Performance Standards

 The filtration efficiency is 0.5 micron

Removal capabilities as follows:

>99% Arsenic 5 and 99% Arsenic 3 (special order)
>99% Hydrogen Sulfide (H2S)
>95% Chlorine and Chloramines
>99% Taste
>99% Odor
>98% Aluminum
>96% Iron
>98% Lead
>90% Pesticides
>85% Herbicides
>85% Insecticides
>90% Rodenticides
>85% Phenols
>85% mtbe
>85% Perchlorate
>80% Trihalomethanes
>95% Poly Aromatic Hydrocarbons
>99.999% of particles larger than 0.5 micron (Staffordshire University Labs) (includes Anthrax)
>99.7% of particles larger than 0.3 micron (Staffordshire University Labs)
>98% of particles larger than 0.2 micron (Staffordshire University Labs)
>100% Giardia Lamblia
>100% Cyclospora
>100% removal of live Cryptosporidium (WRc Standard) 
>100% removal of Cryptosporidium (NSF Standard 53 – A.C. fine dust – 4 log challenge)
>100% removal of E. Coli, Vibrio Cholerae (Johns Hopkins University)
>99.999% removal of Salmonella Typhil, Shigella Dysenteria, Kiebsiella Terrigena (Hyder Labs)

Product is silver impregnated and will not permit bacteria growth-through (mitosis)

provides a hostile environment for all microbiological organisms and will not support their growth

Ceramic elements may be cleaned 100 or more times with a soft brush or damp cloth.

Performance Features:

Easy installation (minutes)

Good flow rate / Up to 1 gallon of clean water per hour (gravity flow)

Up to 300 gallons per hour (pressure flow)

Filter will accept water from floods, lake, rain, well, tap, river or stream

Semi/Annual filter replacement Cleansable with clean damp cloth

For more information: http://www.monolithic.com/stories/a-practical-life-sustaining-water-filter

For a complete free manual on rainwater catchment see http://www.ctahr.hawaii.edu/oc/freepubs/pdf/rm-12.pdf 

Love, David

Illustration and text © 2010 David Kinne – Photos courtesy Monolithic.com

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