Gray Water Systems Abound During Calif. Drought

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As California plans to reduce the amount of water available for residential use, close to a million residents are utilizing gray water systems to reuse water from washing machines and bathtubs for non-drinking purposes around the house.

Gray water is sometimes used as water for gardening. Photo:

Gray water is sometimes used as water for gardening. Photo:

The EPA estimates that a family of four uses 400 gallons of water per day, and gray water is responsible for more than half of this. Because about 30 percent of this water use is outdoors, collecting gray water for outdoor watering represents significant water savings.

The trick for Californians is that gray water systems require permits and regulations, including that the system be buried nine inches under the ground. This is in contrast to states such as Arizona, which only require gray water systems to “ensure safety and no cross contamination.”

California is looking into new rules for gray water, says State Sen. Allen Lowenthal. “The emphasis is —as long as it is safe— to try to use gray water as a conservation tool in California and that is really where we are moving.”

Colorado State University is currently researching the impact of gray water on plant growth to see if it is an adequate substitute for freshwater. One issue with gray water is the remnants of soap or detergent containing salt or boron, which can actually dehydrate plants.

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Trey Granger
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  1. We seem to use a lot more gray water here in arizona than this article is describing. I seen entire collection wells right near farms and other areas. I see it used on the cotton farms here and other such things but in addition to salts and boron arent there other things that might be hazardous when feeding plants gray water and then grow fruits and vegetables and we eat them?
    Btw does anyone ever get a chance to answer these comments or do i really need to post my email addy publically on here?

    1. Hello TriskelionAZ,

      We get a lot of comments each day and are not able to answer them all. If you are looking for a direct response from our readers, feel free to leave your email address. If not, check back often, most of the time others readers will reply to your comment by leaving a comment of their own. Thanks!

  2. I actually use leftover soapy water on my plants to keep the spider mites and some other insects away. I only use earth-friendly soaps and detergents and am currently only growing one experimental vegetable. The rest of my plants (all drought tolerant) are for hummingbirds, butterflies and bees who all seem to be enjoying the garden. I live in California and would like to know more about using gray water.


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  5. We have been using gray water for irrigating lawns and vegetable gardens for over 16 years and am yet to see any negative impacts of using gray water.
    There has been no significant salt build up in the soil and as long as chlorine free and phosphate free laundry detergents have been used we have had great harvests with abundant growth.

    I agree with Kenda that slightly soapy water actually keeps some pests away.

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