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As I write this, the rain pounds on the windows, and the mud thickens in our yard. It's difficult to tell my daughter not to waste water washing her celery when we have just broken the record for the rainiest November in Seattle's history. While the thought of a drought seems remote to me today, even here with our short but dry summers, water needs to be conserved.

During thirsty summer months and year-round in arid climates, a tremendous amount of clean drinking water is wasted. "Lightly used" household water, known as graywater, can be reused for irrigating landscaping by installing a residential graywater system. Even more water can be saved by reusing graywater for activities such as washing clothes and flushing toilets, but its easiest to get a permit for reusing it on landscaping. Graywater reuse lessens the need for developing new water sources and limits groundwater aquifer depletion. "Water will be more important than oil this century," says the former UN Secretary General Boutros Boutros-Ghali; this is especially true as our globe continues to warm. Depending on your local city or health agency requirements, the benefits of graywater can make it an attractive option for your home.

Graywater Defined

Water in our homes comes in three varieties: whitewater or freshwater is the drinking-quality water entering your house (see "Purely Water," Part 1 in Issue #7 and Part 2 in Issue #8); blackwater is the water discharged from toilets; and graywater is the water discharged from sinks, showers, bathtubs, dishwashers and washing machines.

On average, 50 - 80 percent of each household's wastewater is made up of graywater. In U.S. households, graywater is generated through the one-time use of 35,000 - 55,000 gallons of freshwater per year. Graywater is routinely reused in most of the world, especially arid zones. In the U.S., graywater reuse is most common in the southwestern states where the requirements for its use are easy to follow; elsewhere, state and local codes are more complex.

Saving Water
In other countries, people use dramatically less water than in the U.S., ranging from three gallons per day (gpd) in sub-Saharan Africa to 80 gpd in Europe. According to BBC News, "Global water use has tripled since 1950 and has been increasing faster than the world's population. Much of the water extracted ends up wasted." The U.S. EPA, as of 1990, reports that the average person in the U.S. uses an astronomical 183 gallons per day, peaking in the Southwest at 423 gpd. That average includes landscape irrigation, where over 30 percent of freshwater is used on lawns (see Smaller Lawns in Issue #10).. High costs and high chemical and energy use are also associated with water development, extraction, transport, delivery and treatment prior to and following home use. Many wastewater treatment plants are over capacity, and expansion is costly. Reusing graywater considerably reduces water consumption by saving 50 - 100 gpd of freshwater per household and significantly cuts water and sewer bills.

The Legality of Graywater
Australia and the southwestern U.S. states have progressive regulations on graywater use because of their acute water shortages. The states of the southwestern U.S. allow reuse of graywater primarily for landscaping. In both Arizona and New Mexico, a typical household that follows the reasonable precautions summarized below doesn't even need a permit for graywater reuse.

Nearly every state and county has a different regulation regarding graywater. Some have such complex requirements that they make graywater system installation prohibitively expensive. In Washington State, graywater is in the same classification as blackwater and requires septic-system-type treatment. But slowly, changes are beginning to occur.

Changes afloat: Both the continued water-shortage issues and the pervasiveness of unpermitted systems point to the need for new legislation. To make graywater use simpler, more cost-effective and easier to approve, urge your state legislators to enact short, easy-to-follow regulations similar to those in Arizona and New Mexico. In these states, graywater reuse is saving taxpayers millions of dollars on water and treatment-plant development and saving billions of gallons of water.

Even in areas where graywater use is not officially approved, its unpermitted use for irrigation is common during droughts and when water-use restrictions are in place. Since plumbing code violations are difficult to enforce, there is little that can be done to reprimand a homeowner who chooses to create a graywater diversion. In fact, on its website, the U.S. EPA encourages the residential reuse of graywater.

Graywater in your Home
Conservation first: I already use the simplest graywater system there is: tossing my vegetable wash-water out the door, onto deck plants. Using less water is cheaper, easier and safer than installing a graywater system (see Rethinking Water in (Issue #10).

Precautions: The main reason that houses aren't built with graywater systems already installed is that graywater contains small amounts of biological contaminants and nitrogen. Graywater can also include chemicals that homeowners pour down the drain. So use only eco-friendly cleaning products and low-phosphorus dish- and clothes-washing products with environmentally-friendly ingredients such as baking soda or vinegar (see Dirty Laundry in Issue #6 and Naturally Clean in Issue #3).

According to regulations in the southwestern U.S., if several straightforward guidelines are followed for the safe handling of graywater for irrigation, potential health risks will be minimized: Do not drink it or put it on anything that will be eaten, including root crops like carrots and potatoes. Instead, apply it to ornamental trees, shrubs, flowers or fruit trees. Graywater should be applied to landscaping just below the soil surface or at the soil surface. Do not apply graywater using spray or sprinklers; this prevents it from being inhaled. Don't use it to wash walkways, driveways, patios or other areas people often touch. Although these precautions focus on irrigation use, similar precautions pertain to other in-home graywater reuse.

Graywater systems: There are many options for graywater systems, starting with the simplest, which costs $60 - $200 (see the Water Conservation Alliance of Southern Arizona website). It's much easier to build them into new construction than to retrofit. And there are some situations where a graywater system has more limited utility: when there is poorly draining soil or in cold or excessively wet climates.

The Oasis Design website includes the story of Rainy Fackler-Adams, owner of a single-family-home branched drain graywater system in Santa Barbara, California. He reuses graywater from his bathtub/shower, bathroom sink and washing machine. The system is gravity-fed and has no filter or tank. Two irrigation areas in the yard are alternated every couple of weeks so the soil dries out. Graywater seeps into the ground through buried perforated five-gallon buckets surrounded by wood chips. The cost of the self-installed system was $781 ($212 to divert the graywater and $569 to install an irrigation system). Operating costs are low because it is a very simple, gravity-fed system. About one hour per month is spent on maintenance. Rainy says, "Branched drains are the best residential graywater system since indoor plumbing."

Though comparatively expensive because of stringent requirements, a number of residential graywater systems have been installed in Washington State. The State Department of Health (DOH) approves of systems that typically include a 500-gallon holding tank, filtration, a pump and a subsurface drip system (SDS). An SDS slowly distributes the graywater into the shallow subsurface soil through small-diameter piping with small holes (dripline). Graywater is discharged at slow, controlled amounts of about one gallon per hour. Dripline can be installed by hand or machine, similarly to any landscape irrigation system.

Design and Installation: There are four steps in designing a graywater system for your home. Do it yourself if you have the skill, or hire an expert (a professional wastewater engineer or an installer for the system you've chosen).

• Contact your local health officials to get permit and design requirements. They may also give you referrals to qualified designers/installers. Don't be shocked if they've never heard of graywater. Use the resources in this article to educate them about the merit and safety of your project.
• Then count the number of graywater sources in your home (sinks, washing machine, etc.) and use the charts in the books listed in the Articles Archive at www.polishingstone.org to estimate the gpd for each.
• Next, have an expert map your home site (soil type, wetlands, topography, depth to groundwater, buildings, utilities) and estimate the size of the areas to be irrigated.
• Finally, submit an application to your local health officials for approval. Once approved, you're set to install and operate your system.

The easiest graywater systems to install are reasonably-priced ones that consist of PVC piping and fixtures like flow splitters and diverter valves. A flow splitter is typically a two-inch or smaller tee, which divides the total graywater flow. Multiple-flow splitters are used (up to 16) to evenly and slowly distribute the irrigation water. If you are adept at plumbing, you can do it yourself with parts bought at spa- or irrigation-supply stores.

Even in wet climates like ours, I still have angst about clean water going down the drain. At my home, I am looking forward to installing a graywater system for irrigating our fruit trees and native plants; then I'll relax and let my daughter use a bit more water to wash her celery.

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