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Illustration of gray water recycling

How does your garden grow?

With luscious pears drawing envious stares, and peach trees all in a row. It may sound contrary, but recycling wastewater can make your backyard bloom.

by Larry Gallagher

It sounds like the kind of utopian fantasy that sends eyes rolling skyward: Water the peaches while you're taking a shower! Turn laundry water into apples! Feed the fig trees while you brush your teeth! I'd be rolling my eyes too if I hadn't seen it for myself. In fact, I helped build the wastewater reuse system in the backyard of a friend's rental property in California's wine country. All the water from the sinks, tub, showers, and washing machine that would have been flushed into his septic tank is now piped directly to the roots of his fruit trees.

"Gray water" is the term used to describe all the stuff that goes down the drains in your house. Contrast that with the "black" water that flows from your toilet and you will grasp the metaphor. Depending on whose estimate you believe, gray water accounts for 50 percent to 80 percent of the water swirling down our pipes. When curbing water use was not on anyone's mind, plumbing systems were designed and codes were written to merge the gray with the black, sending all of it to municipal sewage plants or septic systems.

Experts may quibble over the extent of our planetary freshwater shortage, but you don't hear anyone predicting that it will be less of a problem in the future. Between falling aquifers, swelling populations, groundwater pollution, and global warming, the thirst for clean water promises to be a major challenge in the years to come. Although the Environmental Protection Agency estimates that domestic use accounts for just 6 percent of all the water consumed in this country (a small amount next to the 81 percent used for irrigation), it is the only portion over which individual consumers have some direct control.

Still, saving water is only one strand in a web of good reasons to reuse gray water. Recycling wastewater will extend the life of your septic system. Or, if you're tied in to a municipal system, scaling back the amount of water you flush into treatment facilities lessens your share of the chemicals and energy used to process your town's water. And in areas where water is tight, recycling gray water could mean the difference between raising tulips and watching tumbleweeds.

I confess: the bulk of my knowledge on this topic comes from the work of one Art Ludwig, founder of Oasis Design in Santa Barbara, California. Ludwig has written a number of small books on the subject, from which I lifted the design for the system that I installed. For a rundown on gray water reuse I picked up Create an Oasis With Greywater, then turned to Branched Drain Greywater Systems to figure out how to put together Ludwig's favorite system. In the course of my reading, I learned that gray water systems are not without potential pitfalls. Improperly treated gray water poses a theoretical threat to public health because we scrub bacteria and viruses, in relatively small quantities, off our bodies during our daily ablutions. And soap dumped directly into water can cause harmful algal blooms.

When installed properly, gray water systems can circumvent these problems, but the environment has to be just right. Ludwig extols the "spectacular" purification capability of organisms in the upper, most biologically active, layers of soil, but balances his enthusiasm with words of caution about the many conditions that render a gray water system undesirable: inaccessible plumbing, an overly wet or cold climate, and unsuitable soil, to name a few. He's also pretty clear about the ways people can be exposed to the health risks of gray water. He advises against spraying the stuff on lawns or gardens, or using it where people might come into contact with droplets before the bacteria are broken down.

Not least among the complications involved in gray water reuse are the legal issues. Gray water law is a confusing patchwork of plumbing codes that vary from state to state and sometimes county to county. At the forefront are Arizona and New Mexico, where reining in water use is an obvious priority. In both states, regulations are based on the amount of gray water a home produces. For example, in Arizona, households that generate less than 400 gallons a day -- well above the national average of 135 gallons -- can install gray water systems without applying for a permit. Arizonans must meet 13 criteria that can be easily satisfied with a system like the one I constructed. Unfortunately, the house I worked on sits in Sonoma County, California, so I was off by a state. Or 25 years, depending on how you look at it. California requires adherence to the gray water appendix of the state plumbing code, which is complicated enough to scare off any layman. But as pressure increases on our water supply, these codes are likely to be updated and simplified to reflect the minimal health threat posed by gray water irrigation.

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When Every Drop Counts

Learn more about gray water: Art Ludwig's books can help you figure out which climates, soil types, and plumbing supplies work best. His books, as well as basic supplies, are available at

If you're not ready to dig up the lawn just yet but are looking for more ways to save water around the house, try capturing rainwater. Building your own rain barrel is fairly simple, and the naturally mineral-free water is ideal for gardens and window washing. For a how-to guide (or to buy one) check out

More Living Green

For other tips on environmentally conscious living from OnEarth magazine, visit the Living Green index page.

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Larry Gallagher uses journalism to fund his musical habit, the results of which can be found at Gallagher also writes for Wired, Discover, and Backpacker. He lives in San Francisco.

Illustration: Craig Larotonda

OnEarth. Fall 2005
Copyright 2005 by the Natural Resources Defense Council