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How to Collect Rainwater

Iowa's Rain Can Supply All Your Water Needs


According to a recent UN report, the next century’s wars will not be about oil, but about water. Fortunately, in this part of Iowa (the southeast), we are blessed with abundant rainfall distributed throughout the year. The question is, how do you collect and use rainwater?

Rainwater is naturally purified and distilled by the sun. The earth’s systems that purify and distribute water as rain are a marvel of nature’s engineering, operating for billions of years without human intervention. We are interconnected to all the waters of the earth by these systems—the cup of tea you drink almost certainly has molecules that were once in Cleopatra’s bathwater.

In southeast Iowa, we get about 35 inches of rain per year on average, fairly evenly distributed through the year. In contrast, a place like San Diego gets only 10 inches of rain a year and it sometimes doesn’t rain at all for 6 months. But even San Diego could supply its water needs from rainwater.

A 1600-square-foot home gets 35,000 gallons of rainwater per year, almost 100 gallons per day. The total amount of rainwater delivered is astounding—the City of Fairfield gets 3 billion gallons for a population of 10,000 (that’s 218,000 gallons per person). Of course, we share water with lots of other life forms, but there is plenty for our needs if we use it wisely.

Most of the water that hits the surfaces of buildings, roads, and parking lots goes unused, and becomes an expense to get rid of. In contrast, many parts of the world require rainwater collection systems. These systems can eliminate the need to mine water from deep in the ground or to set up costly structures to dispose of waste water. Abundance Ecovillage, a new housing project in Fairfield, is designed to use rainwater to supply all the needs of 30 homes, a vegetable farm, and a nursery (

My neighbors and I have been using rainwater for all our water needs for over ten years. It is not necessary to have potable water for most uses. Do you really need drinking water to flush your toilet, for example? We need only a few gallons of potable water a day. Here are some things you can do to use this gift from nature.

Collecting Rain from Roofs and Other Hard Surfaces

The higher your rainwater collection area, the better, because you can use gravity to distribute water rather than using pumps. Gravity is free and never fails. Roof and garage areas work well and often already have gutters. Roof collection systems are often equipped with roof washers, which automatically discard the first few gallons of rainwater each time it rains. You can also collect rain off other hard surfaces like driveways (even gravel driveways are quite impervious to water) and roads. You can collect water by building shallow ditches on contour (called swales) or with a slight slope that leads water to storage areas (ponds and wetlands, for example).You can use existing ditches to collect water.

Storing Rainwater

Once you’ve collected rainwater, one way to store it is in barrels. (Food-grade plastic 55-gallon barrels are available from the Kalona Cheese Factory for $5). You can connect a hose to a barrel with a male garden hose to 3/4-inch male pipe-thread adapter (about $3 at most hardware stores). Find a wood spade bit the same size or just a little smaller than the 3/4-inch male thread, and use it to drill a hole near the bottom of the barrel. Screw the 3/4-inch pipe-thread end of the adapter into the hole in the barrel (the metal adapter will cut threads into the plastic barrel), and apply silicone caulking liberally to the inside and outside.

For less than $10 you can get 55 gallons of storage, and barrels can be connected to get larger amounts of storage. If your barrel is higher than your garden, you can use gravity to deliver the water. Even a few feet above your garden is enough to run most drip irrigation on gravity. Keep the tank screened or add a few goldfish to eat mosquito larvae.

A wide range of reasonably priced water storage containers up to 1500 gallons are available at farm supply stores.

Rainwater can also be stored in ponds. For around $500 you can have a ponddug that will store hundreds of thousands of gallons of water. In a fewhours you can hand dig a pond that will store thousands of gallons of water, and our heavy clay soils mean that you may not need a liner.

Concrete tanks are excellent for storing water. Precast tanks of up to1500 gallons are locally made (Fairfield Precast) and are available for less than 50 cents per gallon. The 10,000-gallon tank in my home cost very little because it was built as part of the basement. To insure an adequate water supply for a typical family of four, I recommend at least 8,000 gallons for a whole-house system.

Porous paving systems can be used to create invisible lakes under parking lots. Millions of gallons of water can be stored under a typical grocery store parking lot in this way.

Treating Rainwater

For most uses, it is not necessary to do any treatment for rainwater. For drinking you can use silver-impregnated ceramic filters like the ones manufactured by British Berkefeld. You can also use solar distillation or pasteurization, sand filters, reverse osmosis, ozonation, UV light, or wetland/living machine systems.

Using Rainwater

Rainwater is great for showering and bathing. Plants like rainwater better than municipal water, which has chlorine and other biocides added. You can use untreated water to flush your toilet or wash your car. Many technologies exist that can help you use water wisely and reduce your consumption by 50 to 75 percent while still getting thesame or better services. Some of these include drip irrigation, low-flow toilets (almost all toilets are low flow these days), appropriate landscaping, and high-tech shower heads that give the same tingly shower with muchless water. Horizontal axis washing machines use one-third the waterand half the energy—and get yourclothes cleaner.

Rainwater is an abundant, high-quality, and versatile water supply. See for photos, references, and more information on rainwater collecting.


RainwaterCollection Over Texas: Service, systems, supplies. San Marcos, TX, Tel: (800)222-3614 collection for the mechanically challenged—book and video
Economic Security for Spaceship Earth, by Jim Bell. Excellent bookby San Diego environmental designer and mayoral candidate Jim Bell. Itdetails how even San Diego could be water self-sufficient with the wise use ofrainwater.
Rainwater Harvesting: The Collection of Rainfalland Runoff in Rural Areas, by Arnold Pacey, Adrian Cullis. Great book, designedfor third-world applications.

For more resources and information, visit Lawrence Gamble’swebsite:

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Comments (1)Add Comment
written by Tom Foolry, January 06, 2012
Great tips! We don't actually have to worry too much about rainwater where we live, because we've got a nice irrigation system that leads from a canal (well, it was a canal, they just covered it). At any rate, could you explain the process of reverse osmosis to me? I've heard the term thrown around and I don't understand it.
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