Leah Drake is a guest contributor for this post. She is a designer with a specialization in water conservation with years of experience in successful California rainwater harvesting and graywater system design and implementation. Learn about her firm at Drake Design Associates. If you enjoyed this post, be sure to also check out our past entry on rainwater harvesting. – New Avenue
These days, many households are seeing the benefits and water savings of putting their graywater to use in the garden. In California, graywater systems for use in Landscape Irrigation have been approved by the State. What is graywater? It is the relatively clean but soapy water that is used in the washing machine, the bath or shower, or lavatory sink. It contains soaps, which have phosphates in them – which many plants love! (There are some plants that do not do well with phosphates, so please check with your landscape designer for a list of plants that LOVE graywater!) The trick to make sure your graywater is earth friendly and does not contain harmful additives is to use eco-friendly varieties of soaps and shampoos, such as those found at Trader Joes or other brand names like Ecover.
How much can a family save in clean, drinking water per year, if using graywater instead of the city or municipal water supply for landscape irrigation? About 10,000 gallons per year per person is the average calculation, if the members of the household are already conservative water users. A household of two can generate 20,000 gallons or more of water a year, which can be enough to irrigate the entire landscape, if it is a typical suburban lot with a low-water using, drought tolerant landscape design (more on this subject in another article.) For a family with kids, more graywater is generated. A family of four can generate up to 45,000 gallons or more per year!
You can see that when planning your new home, it makes sense to put the extra effort to plumbing the bathroom (except the toilet) and laundry fixtures for graywater, if the water savings is this high!
Your graywater system should take into account the possibility of the household not generating enough water for the landscape, say, during a family vacation. This means there should be a back-up plan for irrigating the landscape when you are away. One way to do this is to have your irrigation system automatically turn on the municipal water system should there be no water in the graywater tank.
In order for graywater or recycled water irrigation systems to be approved by the local health department, however, the irrigation system must be subsurface, such as a drip system, not overhead spray. And there must be a backflow preventer to keep the graywater from accidentally flowing into the municipal water line. Another important consideration is that the water must be used within 24 hours, or it will not be easy on your filters or your olfactory system, unless there is an aerator in place.
Graywater systems vary in size, complexity and convenience. See examples. The recommended more complex and automated systems can range from $5,000 to $15,000 to install, but can save tens of thousands of gallons of potable water per year.
Ask your professional Landscape designer who specializes in graywater and rainwater systems for details about the best graywater components and level of automation that is right for you and your landscape!