The simplest water-harvesting system is no more than a single barrel equipped with a valve for a garden hose. (Photograph by Dan Chavkin)
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Using rain barrels is an old concept that has come around again, and with good reason. Water that washes off your roof does nothing but over-water lawn areas near the downspouts, or burden a house's foundation drain system. It also contributes to runoff that carries pollutants into waterways. Why not capture it instead, and put it to work watering vegetables or flowers?

But does it pay? Yes, in terms of environmental stewardship. No, on purely economic grounds. Unless you get a free or low-cost recycled food barrel and fit it with inexpensive plumbing parts, a pair of commercial rain barrels, diverters and perhaps even a pump will cost $300 to $700, depending on the model you choose. They will return somewhere from $3 to about $12 a year in water-cost savings, or maybe a few dollars in electricity savings if you pump water from a well.

These products make more sense in terms of water conservation and reducing polluted runoff. Say you have 1900 square feet of roof surface, not an unusual roof size. That surface will shed somewhere between 12,000 and 24,000 gallons a year, depending on how much precipitation your area receives (a large part of the continental U.S. receives up to 40 inches of precipitation yearly; arid regions may receive less than half that). To put that in perspective, a typical 25-foot, round, aboveground swimming pool is filled to the rim of its 52-inch depth with about 15,000 gallons. Not all of that water falls when you need it, but if a quarter of it does, that's still enough to satisfy a large part of your irrigation needs.

Before installing any system, check with your local building department about what is permitted where you live. Many states have laws that govern rainwater harvesting, even on a small-scale, individual level. Alaska, Arizona, California, Colorado, Idaho, Montana, New Mexico, Oregon, Utah and Wyoming have regions that restrict the practice or require you to file a permit and prove that you're putting the captured water to beneficial use. On the other hand, some states and municipalities encourage the practice by subsidizing rain barrels or providing guidance through websites.

For people who don't want to rig up their own system, new rain-harvesting products are attractive and well-thought-out (for example, It's not the old, half-rotted steel barrel filled to overflowing and swarming with mosquito larvae. Any system should divert the rainwater once the barrel is full. Otherwise the water backs up the downspout to the gutter and overflows. Also, if the barrel is elevated to provide gravity flow, it must be securely fastened so that it cannot tip over and hurt a child. The more thought you give to the system's design before you begin, the better it will work.


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