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System Requirements for Graywater Rebate

Graywater laundry to landscape rebate

Program Requirements

Landscape Requirements

  • All graywater must be gravity-fed and distributed from the clothes washer to a pre-approved landscape area that is large enough to absorb the graywater.

  • Mulch basins are required. Excavate soil around the drip line of the plants to be irrigated with graywater, and backfill the empty space with mulch. For more information on mulch basins, please see the system example hyperlinked at the top of this page or review the Graywater Resources located here.

  • Mulch basins must be sufficiently sized to prevent runoff and pooling of graywater.

    • A specific required square footage of mulch basins will be provided before or upon receiving your Notice to Proceed. This square footage is based on the amount of graywater expected to be produced and the landscape’s soil type.

    • The graywater system may have one or more valved zones. Mulch basins within each zone must meet or exceed the required square footage provided.

  • The site where graywater is used must be in an area where seasonally high groundwater is at least five feet below ground surface. This will be verified by the District using available information.

  • Graywater must:

    • Not be stored, must not runoff into streets and waterways, and must not pond nor pool on the soil surface.

    • Not be used to irrigate root crops or edible parts of food crops that touch the soil.

    • Be contained on the site where it is generated.

    • Be distributed subsurface or released to an area covered by a minimum of two inches of soil, bark, rock, mulch, or appropriate permeable cover.

Graywater System Requirements

  • The graywater system and parts thereof must be on the same lot (parcel) as the building or structure that discharges the graywater.

  • Graywater must be distributed at least:

    • 18 inches from the property line (Note: this minimum distance requirement shall be increased if the adjacent property is downhill from the graywater distribution point(s).);

    • 2 feet from buildings;

    • 5 feet from any septic tank or leach field; and

    • 100 feet from wells, waterways, or other water sources.

  • Graywater piping/tubing and the diverter (3-way) full-port ball valve shall be the same diameter as or larger than the clothes washer drain hose. Typically, 1-inch diameter.

  • The end of the main-line tubing shall be left fully open (allow a continuous unobstructed graywater route from the clothes washer to the landscape; never use a valve or plug on the distribution point furthest away from the clothes washer.).

  • The graywater system shall:

    • Not include a potable water connection, filters, nor a pump. (Note: The pump in a clothes washer is not considered part of the graywater system.)

    • Not connect to overhead (spray) irrigation nor to a conventional irrigation system.

    • Be designed to prevent clogging of any emitters.

    • Be designed and installed to prevent contact with humans and pets.

    • Be labeled on every 5 feet of exposed graywater piping with, “Caution: Nonpotable graywater. Do not drink.” Labels may be provided upon request.

    • Include a diverter (3-way) full-port ball valve to allow the user to direct the flow of graywater between the graywater system and the sanitary sewer/septic system.

    • Include an auto vent (or an in-line vent or an air-admittance valve).

  • The diverter valve and auto vent assembly:

    • Must be installed at least 6 inches above the flood rim (typically the top) of the clothes washer.

    • Must be easily accessible and labeled. Labeling shall indicate which direction to turn the diverter valve’s handle to send graywater to either the landscape or the sanitary sewer/septic system, respectively. Example labeling may be provided upon request.

    • Shall be used to direct to the sanitary sewer/septic system all wastewater derived from activities that could create health issues. These activities include, but are not limited to:

      • Washing diapers or similarly soiled garments,

      • Washing greasy or oily rags,

      • Cleaning car parts,

      • Disposal of waste solutions from photo labs, and

      • Other activities that contain hazardous chemicals.

  • Any perforations in the building created during installation are properly sealed or patched.

  • The finished system must include an operating and maintenance manual. The manual is to remain with the building throughout the life of the system. Upon change of ownership or occupancy, the new owner or occupant shall be notified that the structure contains a graywater system and provided the manual. A template manual may be provided upon request.

  • To facilitate future maintenance, the operating and maintenance manual shall include a diagram depicting the final locations of graywater piping, distribution points, and mulch basins with respect to the property line and landscape.


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