Greywater is waste water from laundry machines, bathroom sinks, showers, and bathtubs. California law does not allow greywater use from kitchen sinks or dishwashers. In January 2010, the California Building Standards Commission adopted Title 24, Part 5, Chapter 16A into the California Plumbing Code, and applies to residential buildings only. The new greywater code facilitates water conservation, relieves stress on private septic systems, makes legal compliance easily achievable, and provides guidelines for avoiding potentially unhealthful conditions. All greywater irrigation systems must comply with the following guidelines to protect the environment and avoid system failure:
■ Any greywater system that includes a connection to a potable or municipal water supply must have an approved, backflow prevention device. Laundry to landscape greywater irrigation systems that are exempt from permitting must have no connection to the potable water supply or an external pump.
■ The greywater system design must include an accessible, clearly labeled, three-way valve that diverts the greywater back to the building sewer. Greywater should be diverted to the building sewer during the rainy season between November and April.
■ The greywater must not leave the property where it came from or come within 100 feet of any creek, wetland, or waterway.
■ The groundwater table must be lower than 3 feet from the lowest greywater irrigation or disposal point.
■ Each release point of the greywater irrigation system must be covered with at least 2¨of mulch, rock, soil, or a soil shield. Sprinkler irrigation and ponding of greywater are not allowed!
■ Water used to wash diapers or other infectious garments must be diverted to the building sewer.
■ Greywater may not contain hazardous chemicals.
■ Greywater may not be used to irrigate root crops or other edible crops that touch the soil.
■ An operations and maintenance manual for the greywater system must be provided by the installer and must be transferred to the new tenant or owner for the life of the greywater system.
■ Greywater irrigation systems must be located a minimum horizontal distance away from the following landscape features:
|Landscape Feature||Minimum Horizontal Distance from Greywater Irrigation System|
|Building structures||2 feet (610 mm)|
|Property line adjoining private property||1.5 feet (458 mm)|
|Water supply wells||100 (30,480 mm)|
|Streams Rivers,,Lakes, Wetlands, and High Tide line of Ocean||100 ft (30,480 mm)|
|Sewage pits or cesspools||5 (1,524 mm)|
|Sewage disposal field||4 (1,219 mm)|
|Septic tank||5 (1,524 mm)|
|Onsite domestic water service line||0 (0 mm)|
|Pressurized public water main||10 (3,048 mm)|
For detailed information regarding required setbacks for greywater tanks, greywater irrigation fields, and greywater disposal fields, see Table 16A-1 of Title 24, Part 5, Chapter 16A of the California Plumbing Code.