Tap into Water Savings

Image Gallery This handsome garden in Santa Barbara is a state of California graywater test site. The garden’s fruit trees and perennials have benefited from trouble-free graywater irrigation for almost 20 years.

by Claire Anderson

Last summer, almost one-third of the United States suffered moderate to extreme drought conditions, leading many counties to limit lawn and garden watering. Water utilities redoubled their conservation education efforts and, in some cities, police fined wanton waterers — folks who surreptitiously sprinkled their lawns despite citywide bans.

Those homeowners probably did not know they had an untapped resource: 1,000 to 1,500 gallons of “graywater” per week are shunted down the drain by an average four-person U.S. household.

This nutrient-laden wastewater from bathroom sinks, showers, bath tubs and clothes washers is a frequently untapped resource for watering gardens, lawns and fruit trees. Graywater does not, however, include toilet wastewater (also known as blackwater), which may contain high levels of bacteria and viruses.

Shades of gray

You can put this gray “gold” to good use in your own landscape. Graywater systems range from the rudimentary — dishpan water used to water trees — to the complex — graywater fixtures connected to a network of pipes in your landscape. Your irrigation needs, budget, and local plumbing and health codes will guide your decision regarding which type you can install.

Graywater systems can be retrofitted to existing plumbing, although the ease with which this is accomplished depends on where your plumbing lies. Homes with basement or crawl-space access to pipes usually are the least expensive to retrofit. Your local plumber can help you determine your home’s suitability and recommend options. If replumbing below floor level is not feasible, consider tapping your clothes washer, and routing that graywater to your thirstiest trees and shrubs. (For more information, see “Graywater Resources,” Page 106.)

Meet your needs

In a household that practices no water conservation, wastewater production from sinks, washing machines and bathroom showers averages nearly 400 gallons per person per week — enough water to maintain a 400- to 800-square-foot flower garden or small orchard. A close examination of your monthly water bills (outside of the irrigation season) can give you a rough idea of how much graywater your household produces. Be sure to subtract about one-third of your total gallons to account for blackwater (if you use a low-flow toilet, subtract about one-quarter). For a more accurate estimate, select the graywater sources you plan to use and use the chart above to determine how much wastewater you produce per week.

Your landscape’s irrigation needs will depend on the area’s climate, soils and plant types. Graywater systems designer and author Art Ludwig says, “Graywater systems are extremely context specific because of the number of variables involved. Each of these variables has the potential to change the design completely.” In all cases, Ludwig counsels homeowners to “choose the simplest design possible and build it the best you can.” (For more details on calculating household graywater production and irrigation needs, we highly recommend Ludwig’s book, Create an Oasis with Greywater; see Page 111 to order.)