Harvesting rainwater is an ancient practice that's seen a revival in recent years. In developing countries, where people often hoof it for H2O, it's attractive because relatively simple and inexpensive systems can provide clean water for a household or even a community. In industrialized nations, it's attractive because it reduces stormwater runoff and eases homeowner water bills.
A typical harvesting system has three basic parts:
- a catchment surface
- gutters and downspouts
- a storage tank
Luckily, most modern houses come equipped with a catchment surface -- the roof -- and an adequate supply of gutters and downspouts (although one critical addition for rainwater harvesting is a system of filters and screens to keep debris out of the water supply). That leaves the storage tank, or cistern. In more sophisticated systems, cisterns can be large structures made from concrete or galvanized steel, sometimes located underground, sometimes not. Simple, homebuilt cisterns, however, are both possible and extremely functional.
The most basic designs use plastic barrels for water storage. A popularchoice is a 55-gallon (208-liter) barrel made out of high-density polyethylene, or HDPE, plastic, although even Rubbermaid trash cans can be transformed into an effective, albeit small, storage tank. Either way, the barrel must be opaque to prevent algae growth.
After that, it's a simple matter of retrofitting the container so it can function as a water collector. This may involve drilling two holes, one at the bottom to hold a faucet and one at the top to act as an overflow valve. Then you cut a hole in the top of the barrel, near the back, to receive a downspout. Attach some window screen over this opening to catch debris and foil pesky mosquitoes, and you have a perfectly serviceable rain barrel -- and a ready supply of water for gardening.