Washington Administrative Code
Title 246 - Health, Department of
SEWER SYSTEMS
Chapter 246-274 - Greywater reuse for subsurface irrigation
Section 246-274-300 - Tier 3 greywater irrigation systems

(a) Reuses dark greywater;

(b) Involves storage of greywater for more than twenty-four hours;

(c) Irrigates a green roof;

(d) Serves a high public exposure area such as a playground or sports field; or

(e) Is otherwise deemed by the local health officer to require treatment to protect public health or water quality.

(a) The greywater may be light or dark greywater.

(b) The total flow of greywater must be less than three thousand five hundred gallons per day.

(c) The greywater may originate from a residential or nonresidential building.

(d) The building must be served by an approved public sewer system or large on-site sewage system, except as provided in subsection (e) of this section.

(e) If the building is served by an approved on-site sewage system with design flows of less than three thousand five hundred gallons per day, the greywater must originate from a single-family residence and the total flow of greywater must not exceed three hundred gallons per day. If the building is something other than a single-family residence, the local health officer may allow the use of a Tier 3 system if he or she determines that applicable requirements can be met.

(f) Application of the greywater must be even throughout the irrigation field. This is typically achieved through pressure distribution.

(g) Warning signs must be visible at each fixture from which greywater is diverted at a nonresidential building. The signs must notify the employees and the public that water from the fixture is reused for subsurface irrigation of plants and that chemicals and other hazardous materials may not be poured down the drain.

(h) The owner shall maintain a record of the Tier 3 system that: