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PDFWAC 246-274-011

Greywater irrigation systems—General requirements.

(1) The following conditions and restrictions apply to all tiers of greywater irrigation systems:
(a) The greywater must be used only for subsurface irrigation.
(b) The greywater may be used for subsurface irrigation of plants that produce food but must not come into contact with edible portions of any plant.
(c) The greywater must consist of domestic type flows having the consistency and strength typical of greywater from domestic households.
(d) The greywater may not contain toxic substances, cleaning chemicals or hazardous household products derived from the waste from a water softener, activities such as cleaning car parts, washing greasy or oily rags or clothing, rinsing paint brushes, or disposing of waste solutions from home photo labs or similar hobbyist or home occupation activities, or from home maintenance activities.
(e) The greywater may not contain water used to wash diapers or similarly soiled or infectious materials.
(f) The greywater may not contain biomedical waste as defined in chapter 70A.228 RCW.
(g) The greywater may not surface in any way, including through ponding or runoff. It must remain below the surface of the ground so that people and animals do not come into contact with it.
(h) The greywater must be used and contained within the property boundary of the building it originates from or on nearby property where it is legally allowed to be used.
(i) The system may be used only during the growing season.
(j) The system must be located in suitable soil.
(k) The system must be located where the land is stable.
(l) The system may not be located in an environmentally sensitive area, as determined by the local health officer.
(m) The irrigation rates may not be greater than the evapotranspiration rate of the irrigation field.
(n) The system must include a readily accessible diversion valve so the greywater can be directed into the approved public sewer system or on-site sewage system when necessary; for example, when soils are saturated or frozen, or blockage, plugging, or backup of the system occurs, or the maximum allowed gallons per day is reached, or when the building owner chooses not to use the system.
(o) The diversion valve must be visibly labeled.
(p) Pipes and above-ground tanks must be labeled with the words: "caution: nonpotable water, do not drink."
(q) If mulch is used, it must be permeable enough to allow rapid infiltration of greywater.
(2) The location of the system must meet the minimum horizontal setback requirements established in WAC 246-274-405, Table I.
(3) If the system fails or is suspected of failing, the owner shall immediately divert the greywater to the approved public sewer system or on-site sewage system serving the building as required under WAC 246-274-445.
[Statutory Authority: RCW 43.70.040 and 2020 c 20. WSR 22-07-025, § 246-274-011, filed 3/9/22, effective 4/9/22. Statutory Authority: RCW 90.46.015. WSR 11-02-011, § 246-274-011, filed 12/28/10, effective 7/31/11.]
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