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.
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.