Graywater Do’s and Don’ts

A potential silver lining to California’s lack of rain clouds may be that many Californians are rethinking their relationship with water. Many people are looking for methods to conserve water and use water more efficiently. One method that has gained popularity is using graywater for irrigation.

While different definitions of graywater exist, the California Plumbing Code includes wastewater from bathtubs, showers, bathroom sinks, clothes washing machines, and laundry tubs as being sources of graywater. Wastewater from toilets, utility sinks, kitchen sinks, or dishwashers is considered blackwater and cannot be used for graywater systems. Just as there are many definitions of what water sources constitute graywater, there are different ways graywater can be utilized for beneficial uses like outdoor landscape irrigation water.

A common method of using graywater is by diverting laundry wash water to an irrigation system that is below a covering like mulch (e.g. sub-surface distribution). Often referred to as laundry-to-landscape, this method of diverting graywater can be a great way to reduce your use of drinking water. Most building departments do not require a permit to install this type of simple graywater system, and a laundry-to-landscape system can be relatively low-cost to install.

To have a successful graywater system, it is important to understand how to use this water source safely. Some considerations should include:

  • Use graywater for sub-surface irrigation where distribution lines are covered by a material such as mulch. If you intend to use graywater for uses other than sub-surface irrigation, please consult with your County’s Environmental Health Department in addition to your local Building Department.
  • Hire a professional graywater installer.
  • Learn about safe graywater system installation if you can’t hire a professional installer. Organizations such as Greywater Action offer courses about graywater installation.
  • Avoid storing graywater for more than 24 hours.
  • Understand your watering needs including how much and how often plants need to be watered. It is important that graywater does not pond runoff your property.
  • Use detergents and other household products that do not contain salts, boron, or other chemicals that may be harmful to plants.
  • Limit use of graywater to fruit trees or non-edible plants.
  • If you are washing heavily soiled items such as diapers, the water should be diverted to the sewer.
  • Prevent connections to your home or building’s drinking water system.

For more information about using alternative water sources like gray or rainwater, please call (650) 372-6200 or visit http://smchealth.org/alternativewater.

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