Diagrams courtesy of Steve Sanford from the Water-Wise Home
Branched drain system. Shower water here irrigates six fruit trees. Fractions show how the
flow splitters divide greywater flow into halves, quarters, and eighths.
The Laundry to Landscape system is the easiest to set up and no permit is required.
Just for the record, Greywater has been legal in California since 2009.
Developing a greywater system today is a bit more complicated than it was before it became legal and regulations were created. Even so, conscientious Topangans, eager to be good stewards of natural resources, who have already installed, or would like to install a greywater system, may be curious about: 1) Common greywater systems, 2) What to do with greywater, and 3) Some general rules to follow. Fortunately, there are a number of resources available, Greywater Action being one.
There are some questions and possible misconceptions that should be addressed—such as system design, existing/failing systems, disposal of greywater and legality—that we can clarify here.
What, exactly, is greywater? As soon as water goes down a fixture’s drain, it becomes greywater. This excludes water from your toilet, kitchen sink, dishwasher, or any water containing dirty diaper wash, harsh chemicals, paints, solvents, etc. Greywater is not potable but is perfectly fine for watering plants. There are a couple of things to keep in mind when doing this so as to keep the system legal and respect our ecosystem. This is not an exhaustive list, but these are some of the most common and functional systems we know about.
What kinds of systems are there?
Laundry to Landscape—These are the easiest to set up as there is no requirement for a permit and they are quite flexible during installation. They work by using the washing machine’s pump to push water to the landscape. There are limitations to this as the small pumps can’t push uphill and shouldn’t go much farther than 50 feet, unless going down slope. Materials include PVC pipes, PolyEthelene tubing, and a diverter valve to choose whether to send water towards the landscape or to the septic system.
Branched Drain—This system does need a permit because it involves cutting into the existing plumbing to separate and redirect greywater to the landscape. Also, the plants to be watered must be downslope from the greywater source as these drains rely solely on gravity. As the name implies, this design works by progressively splitting the pipes in two to form a branched shape. Materials used are ABS rigid pipe, a diverter valve and ideally an actuator (electric motor) mounted on the diverter to remotely switch valve positions. Usually, the valves are in crawl spaces so you don’t want to go there to switch it before a shower.
Pumped system—Great for pushing greywater up slopes and very versatile, these systems can do a lot but cost more, are more complex and harder to obtain the permits. The greywater flows into a transfer tank with an effluent pump inside and should be emptied shortly after. Greywater should never be stored for more than 24 hours as it will become septic. The catchment area of the system inside the home is the same as a Branched Drain. The transfer part of the system—in the landscape—resembles that of Laundry to Landscape.
How do we water the plants? After the systems collect and divert greywater to the landscape, the journey is not over. We still need to get the water where it will do most benefit, the plants themselves. This is done by sending the greywater to mulch basins next to the plants. A mulch basin is a trench, not usually deeper than 18” and about as wide, filled with wood chips. These wood chips, or mulch, act as a biological filter and also help keep the greywater away from animals, mosquitoes, and humans. The greywater exits into a standard landscaping valve box so roots don’t clog the outlets. All this is located near the root zones of the plants, so they can easily get access to it. A word of caution; greywater has lots of nutrients that plants benefit from, but these same nutrients could easily harm our ecosystem. Please never use Greywater for spray irrigation, allow it to pond, runoff or be discharged directly into or reach the creek.
What types of products should be used? Because the greywater will be going to your plants, we want to make sure there is nothing in the water that can harm them. Don’t use products that contain salts/sodium, boron/Borax, or chlorine. Also avoid sodium-based water softeners as the high level of salts will damage your plants in the long run. Use potassium-based alternatives. Some good products include: ECOS, Biopac, Trader Joe’s, Oasis, Vaska, Aubrey Organics, hydrogen peroxide bleach (oxygen bleach).
Is it really legal to have a greywater system? The answer is… It depends! If you follow the California Plumbing Code, then it is 100 percent legal. If, like anything else, you don’t follow regulations and/or don’t get a permit when required, then it is illegal. For each system, except for Laundry to Landscape, a permit from the Department of Building and Safety is required, as is a plan review from the Los Angeles County Department of Public Health.
Greywater Action is a collaborative of educators who teach residents and tradespeople about affordable and simple household water systems that dramatically reduce water use and foster sustainable cultures of water. Through hands-on workshops and presentations, it’s led thousands of people through greywater system design and construction and work with policymakers and water districts to develop codes and incentives for greywater, rainwater harvesting and composting toilets. The organization believes that decentralized conservation measures can play a critical role in drought resilience, climate adaptation and the return of healthy stream ecosystems.
Sergio Scabuzzo is one of Greywater Action’s educators and currently lives in Topanga Canyon where he spends most of his free time talking about water harvesting, sustainability and plants. For more information contact firstname.lastname@example.org or join the forums at www.greywateraction.org/forum.