Gray water systems: What they are, how they work

Until recently, gray water had the patina of being on the fringe or new age. And it seemed, therefore, dismissible. But that image is changing. As the need to conserve water drives innovation and demand, gray water is finding a place in landscapes and gardens throughout the Bay Area.

Gray water — some types of household waste water that bypasses the sewage system and is piped outside to the garden — is becoming more of a fixture in landscape and architectural designs, embraced by gardeners, environmentalists and homeowners. The reuse system, says Teresa Eade, an 18-year veteran and senior program manager with Alameda County’s Waste Management, now is a recommended practice in Waste Management’s Bay-Friendly Landscape Guidelines.

Brent Bucknum, founder of the Oakland ecological engineering firm Hyphae Design Laboratory and the community-based nonprofit the Urban Biofilter, says gray water systems make economical and environmental sense.

“Gray water is the most affordable, climate-specific solution to water issues in most Mediterranean California ecosystems,” Bucknum says. “It provides a year-round water supply with the smallest footprint, the fewest upfront costs and the least permitting hurdles.”

Gray water systems can save a typical California homeowner 15,000-50,000 gallons of water per year, Bucknum says, and should be a first step to water conservation and reuse.

Although gray water has been legal in states such as Texas and Arizona for years, it only became legal in California in 2010, due to health concerns over pouring “dirty” water on the landscape.

Spurred by the Legislature, the Department of Housing and Community Development took a look at gray water policies and proposed the adoption of less restrictive regulations. The California Building Standards Commission adopted changes to the California Plumbing Code to make installing certain types of gray water systems in residential situations, some without a permit, legal.

Laura Allen, founding member of Greywater Action, says the average homeowner can be mystified by their plumbing systems, and most of us have only a murky understanding of gray water.

“When I realized that by using water in my home, I was participating in a giant infrastructure that extended to a dam 100 miles away, destroyed rivers to send the water to my house and then went through a chemical and energy intensive treatment process to be dumped into the Bay, I decided there must be a better way to do things,” Allen says.

Gray water is wastewater that comes from washing machines and bathroom tubs, showers and sinks. It does not include water from toilets, kitchen sinks or dishwashers, which all produce “black water.”

Babak Tondre with EcoHouse in Berkeley, leads a workshop in laundry-to-landscape gray water systems Courtesy of EcoHouse ( EcoHouse )

An average family of four produces more than 38,000 gallons of gray water per year, says John Russell, a landscape contractor and owner of WaterSprout, an Oakland design-build company focusing on gray water and rainwater catchment systems.

Gray water systems can be complex and innovative — the field is rich with experimentation, research and development — or simplified systems that many homeowners can install on their own after taking a workshop.

There are two basic types of simple systems that handy homeowners can install with a little instruction.

Laundry-to-landscape, which does not require a permit, diverts water from clothes washers to the garden. Branched drain systems divert bath and bathroom sink water by separating it from toilet water and then sending it to the garden. The branched drain systems require a permit, available through city and county building departments.

Both systems need little maintenance and are suited to homeowners with little time on their hands.

Codes governing gray water systems require the water to be drained into a mulch or gravel basin, where it can infiltrate the soil. This prevents ponding or runoff, which is a health hazard. The nutrients carried into the basin with the gray water are broken down by beneficial bacteria and become plant food.

As it turns out, gray water systems fit into the mulched garden trend that is replacing lawns and heavily irrigated gardens. The mulch basins provide a moisture reservoir for plants, which are grown in beds in or around the basins. The code allows a mulch basin to be around a tree, a trough along a row of plants or other shapes necessary for irrigation or disposal. This permits a lot of creativity in incorporating the basins in the landscape. Essentially, they disappear under mulch.

While designers and homeowners are busy planning their gardens and basins, some people still question the safety of the systems. But like most things, the answers lie in education.

“I believe that gray water systems are appropriate for individuals who receive the necessary education and training to properly use and maintain their systems,” says Manuel M. Ramirez, the environmental health manager with the City of Berkeley. “Most systems, if properly located, designed, constructed and maintained, will work as intended.”

Jon Bauer, co-founder of Greywater Alliance and an employee of East Bay Municipal Utility District, is just the kind of educated consumer Ramirez hopes to see install a gray water system.

“I advocate following the rules set forth in the code. They are there to guide you to doing it right,” says Bauer, who installed the first permitted branched drain type system in Oakland at his home after the code changes went into effect a year ago.

He also installed a laundry-to-landscape system, which does not require a permit.

“Once gray water is installed and running and the city has completed the inspection, what they are mainly concerned about is that if I sell the house, the next residents understand the system,” Bauer says. “So I have a one-page instruction sheet that goes with the system.”

The key to gray water system’s safety is the mulch pits or basins, which must be at least 2 inches deep but can be much deeper.

“Healthy soil microorganisms in a garden will gobble up any pathogen that happens to be in gray water,” says Christina Bertea, a plumbing contractor and member of Greywater Action.

There are no known documented illnesses caused by gray water, Bertea says. In preparing to create the gray water codes, researchers scoured reports looking for evidence of any disease outbreak attributed to gray water in this country, and found none.

Gray water may actually improve public health, some say, because it can lead to changes in household practices.

“Using biocompatible soaps and personal care products is key to stopping the pollution of our waters and soils,” says Dig Cooperative’s Nick Bertulis, who teaches a class on gray water at Merritt College in Oakland.

When homeowners realize that the products that go down their drain are now going into their backyard soil where their kids play, Russell says, they become much more interested in the products they are using.

For her part, Allen has found it easy to convince residents to make the switch.

“Everyone I’ve worked with has happily switched over to Earth-friendly soaps and detergents,” she says.

There’s another synergistic benefit, she says. Earth-friendly products contain biodegradable compounds, nutrients and organic matter, which are broken down by soil microorganisms and turned into plant food. So your new eco-friendly laundry soap can double as your fertilizer.

Jillian Steinberger is the owner and operator of the Garden Artisan. Contact her at


  • Do install signage around gray water irrigation systems and label all pipes clearly.
  • Do turn system off during wet weather.
  • Do test your backflow prevention device annually, and do all necessary maintenance.
  • Don’t store gray water for more than 24 hours — it will become black water.
  • Don’t let hazardous chemicals, toxins or wash water from baby diapers into your gray water.
  • Don’t allow gray water to pool or run off, and don’t site it within 100 feet of a creek, wetland, waterway or well.
  • Don’t ingest gray water, and wash your hands after contacting it. Don’t swim in it.
  • Don’t use gray water in playgrounds or recreational facilities.
  • Don’t wash pets in gray water nor allow them to drink it.
  • Don’t allow gray water to pond or run off the property.
  • Do use Earth-friendly cleansers so as not to send toxins and salts or boron to the soil.
  • Do visit websites such as Environmental Working Group’s Cosmetic Safety Database ( and the FDA’s product information website (


    For Do-it-Yourselfers
    Greywater Action, — Statewide affordable workshops and list of installers.
    California Native Garden Foundation — This nonprofit group offers classes, lectures, and workshops on gray water, water-wise gardening, native garden design and growing native edibles. Middlebrook Gardens, 76 Race St., San Jose; 408-292-9993; e-mail
    Common Ground, — Santa Clara-based group onnected with John Jeavons who founded Ecology Action in Willitts, the well-known “biointensive” method of growing edibles.
    Green San Mateo County,
    Oasis Design, — Site of Art Ludwig, known as the “Grandfather of Gray water,” Santa Barbara.
    San Francisco Public Utilities Commission, — Residents will soon have access to free training and parts paid by the commission through the Urban Farmer Store, The commission is also putting out a gray water manual.
    Greywater Alliance,, Recycled Water Information Center,
    California Building Standards Commission, California Plumbing Code,

Comments are closed.