Graywater is untreated wastewater that has not been contaminated by toilet or bodily wastes. Graywater includes water from bathtubs, showers, bathroom sinks, clothes washing machines, and laundry tubs, but does not include water from kitchen sinks or dishwashers.
Graywater Use Conditions
The Easiest Graywater System
Laundry to Landscape Graywater Systems
Types of Graywater Systems
There are three types of graywater systems defined in the California Plumbing Code. Each type of system has specific rules and, depending on the graywater system you use, City and/or County permits that may be required.
|TYPE OF SYSTEM||PERMIT REQUIREMENTS|
|Clothes Washer System|
|A graywater system utilizing only a single domestic clothes washing machine in a one- or two-family dwelling. This method cannot use a secondary pump, relying instead on the washing machine pump or gravity to irrigate the garden areas.||No construction permit required if conditions in California Plumbing Code Section 1602.1.1 are met.|
|A graywater system serving a one- or two-family dwelling with a discharge of 250 gallons per day or less. Simple systems exceed a clothes washer system.||Construction permit and plans required. Construction permits require a plot plan with supporting data, drawings and plans of the graywater system, and a site test by the agency after installation. If drip emitters are not used a percolation test will be required as well.|
|Graywater systems that discharge over 250 gallons per day. Capturing the water requires separate drainlines for the fixtures and appliances generating the graywater. A system to temporarily store the graywater is necessary, along with a pump to convey the graywater to the desired location. Separating the drainlines is relatively easy during new construction, while retrofitting an existing home can be very expensive.||Construction permit and plans required. Construction permits require a plot plan with supporting data, drawings and plans of the graywater system, and a site test by the agency after installation. If drip emitters are not used a percolation test will be required as well.|Basic Graywater Guidelines
- Don't store graywater for more than 24 hours. If you store graywater, the nutrients in it will start to break down, creating bad odors.
- Minimize contact with graywater. Graywater could potentially contain a pathogen if an infected person’s feces got into the water, so your system should be designed for the water to soak into the ground and not be available for people or animals to drink.
- Infiltrate graywater into the ground, don't allow it to pool up or run off. Knowing how well water drains into your soil (the soil percolation rate) will help with proper design. Pooling graywater can provide mosquito breeding grounds, as well as a place for human contact with graywater.
- Keep your system as simple as possible—avoid pumps and filters that need upkeep. Simple systems last longer, require less maintenance, require less energy and cost less money.
- Install a 3-way valve for easy switching between the graywater system and the sewer/septic.
- Match the amount of graywater your plants will receive with their irrigation needs.