(1) A Tier 3 greywater irrigation system is a system that uses a treatment component.

(2) A treatment component is required when the system:

(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.

(3) The following conditions and restrictions apply to Tier 3 systems:

(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:

(i) Shows the location of the system;

(ii) Identifies the fixture(s) that are the source of the greywater;

(iii) Describes the design of the system and how it meets the requirements of WAC 246-274-410 and 246-274-415;

(iv) Identifies the person responsible for designing the system;

(v) Describes the maintenance requirements of the system; and

(vi) Includes an estimated calculation of the total irrigation area pursuant to WAC 246-274-415 (1) and (2).

(4) The building owner shall obtain a permit from the local health officer, in accordance with WAC 246-274-425, before installing the system.