Graywater Clarified

by Ken Foster

In California we spend about 20 percent of our overall energy dealing with water. The term "watergy" was coined to refer to the energy we spend on H2O, making it potable and keeping it flowing. With a graywater system you can help minimize watergy use, conserve your money and the water itself by irrigating landscape and garden plants from the water that comes out of your washing machine, etc.

To be specific, Graywater is used house-water from all sources: shower, bathtub, bathroom sinks and laundry. It is so named to differentiate from the "backwater" that comes from toilets and kitchen sinks. Often the easiest graywater system to install is "Laundry to Landscape." This type of system cuts into the line going from your laundry to the sewer or septic, and pipes it to "mulch basins"—18x18-inch holes dug in the soil and filled with wood chips, strategically placed in the landscape. There it safely infiltrates into the soil, irrigating garden and landscape plants.

Thanks to Arnold Schwarzenegger, the State of California plumbing code has guidelines on how to install safe graywater systems. As long as the twelve basic guidelines are followed, no permit is needed for Laundry to Landscape Graywater Irrigation Systems. A permit is still needed when any change is made to the household drainage plumbing.

No deaths have ever been reported from the use of graywater ;-). However it is wise to prevent possible contamination that can be caused by above-ground pooling. With the state guidelines, graywater never sees the light of day or the inside of a storage tank. Storing graywater is a not a good idea—within 24 hours it turns from grey to blackwater.

Watergy goes local.

The process of a laundry to landscape system is straightforward. When the wash and rinse cycles are complete the water is directed via a three way valve installed right next to the washing machine. This gives you the option of diverting the water back to the sewer or septic if needed for any reason. For example: if you are going to use bleach in the laundry or the ground is saturated from rain you would divert the graywater away from the landscape with this valve.

Next: it is important to install an auto vent. This 'air admittance valve' is to let air into the pipes to break the siphon of the laundry machine pump. The auto vent is always placed at least six inches above the fill line of the washing machine.

The graywater flows through one-inch poly tubing out to the landscape, where it is dispersed at multiple mulch basins. The number of mulch basins depends on what size the wash load is and how many loads are done per week. Between five and 10 mulch basins is typical. Each mulch basin has a manual shut off valve so you can choose where the water is dispersed.

To make the Graywater friendly to plant and tree roots it is important to only use laundry soaps that have no salts, chlorine bleach, dyes or chemical scents that can be harmful to plants. Here are a few examples of ‘Greywater’ friendly laundry soaps: Oasis Laundry Detergent (liquid), ECOS liquid detergent, Vaska, and Dr. Bronners liquid soap. Vaska also makes a commercial laundry detergent that is compatible with commercial washing machines.

Finally it is advised that graywater not be used directly on leaf vegetables, root crops or grass for that matter. A mulch basin near the root zone of a fruit tree is a good example of the best use of greywater.

As you reduce water consumption, using a graywater system allows you to water even as you mind landscape water restrictions. I hope this clarifies your graywater (questions).

Ken Foster is the owner of Terra Nova Ecological Landscape. Right now and for the rest of March he's offerering a $50-off deal on the installation of a laundry to landscape system .
Call to schedule a free estimate: 831-425-3514