Green City: Gray-water guerillas

Recycling water, under the radar
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sarah@sfbg.com

GREEN CITY The task sounded simple: help our friend Kristal set up a bathtub in her backyard over the Labor Day weekend so she could soak under the stars and her plants could drink the gray water.

Gray water is water from the sink, shower, bathtub, and washing machine, but not the toilet. And I've been inspired by its use since reading gray-water guerrillas Laura Allen, July Oskar Cole, and Cleo Woelfle-Erskine's book Dam Nation: Dispatches from the Water Underground (Soft Skull, 2007).

Allen, Cole, and Woelfle-Erskine describe how to install fairly radical gray-water systems, including dry and composting toilets and rainwater capture zones, as well as ways to recharge groundwater with rain gardens and treat gray water using homemade wetlands.

Installing gray-water systems usually requires government permits, and public health officials caution that flawed systems can spread disease and contamination. But our system was a simple one meant to dispose of clean hot water that cascades from the tub into a lava rock–filled drainage ditch that will hopefully, in time, support a small wetland.

Like many Californians, Kristal can only afford a tiny place, but she has hit the rental jackpot with her latest abode. It's a barn red, vine-covered cottage behind a bigger house, but it comes with a private yard, thanks to artfully placed trellises and interwoven tree branches.

The only downside of her cottage is the absence of an indoor bathtub, so Kristal decided to set up a cast-iron bath outdoors and fill it with water piped by a hose from her sink. We tried it out July 4, and it was magical looking at the fireworks while sitting in steaming water that wasn't steeped with hot-tub chemicals.

But when Kristal let out the plug, the gray water splattered out noisily and created an unsightly, muddy hole in the yard. This growing mess got Kristal worried that she would attract mosquitoes, kill her plants, and rot her cottage foundations. So I decided to help, relying on the gray-water guerrillas' manual and my husband's years of experience in restoring wetlands. Together, the three of us talked through the science, economics, and aesthetics of the proposed project to come up with a viable plan.

The science was simple but critically important, given that we were contemputf8g creating a homemade wetland near other dwellings and gardens. Water flows downhill and follows the path of least resistance, while wetlands, which are nature's water purification system, create breeding grounds for native plants, insects, and animals. As such, they are fragile ecosystems that are easily harmed by bleach, bath salts, and any boron-containing products. So it's critical to use all-natural, biodegradable soaps in a tub whose gray water will flow into homemade wetlands.

We reconciled these principles with Kristal's need for inexpensive materials, her love of simple designs, and her desire to camouflage unsightly plumbing. In the end, we settled on a cascading system that uses cinder blocks to elevate Kristal's tub and a wine barrel to hold the gray water, which flows by gravity into the barrel and then into the wetlands.

To control and direct water flow, we linked the barrel by way of a garden hose to a piece of slotted, corrugated drainage pipe. We buried the pipe in a lava rock–filled trench that was dug in a serpentine shape so that the gray water flows away from homes and into the lowest part of the garden, which is filled with sandy, drainage-friendly soil.

After a hard weekend of work, Labor Day found us basking in a freshly painted and elevated aquamarine bathtub, imagining how great Kristal's wetlands will look once she adds water-loving plants like native cattails, which will attract a host of dragonflies, frogs, and beetles. Then we pulled the plug and waited anxiously for the tub to drain.

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