The definitions in this section apply throughout this chapter unless the context clearly requires otherwise.

(1) "Evapotranspiration rate" means the sum total of plant transpiration, evaporation off of the soil surface, and water used for plant growth.

(2) "Failure" means a condition of a greywater system or component that threatens the public health by creating a potential for contact between greywater and the public. Examples of failure include:

(a) Greywater on the surface of the ground;

(b) Greywater leaking from a storage tank;

(c) Inadequately treated greywater reaching ground water or surface water;

(d) Noncompliance with the installation permit; or

(e) Other noncompliance with the requirements of this chapter, as determined by the local health officer.

(3) "Green roof" means a roof of a building that is partially or completely covered with soil and vegetation.

(4) "Greywater" means domestic type flows from bathtubs, showers, bathroom sinks, washing machines, dishwashers, and kitchen or utility sinks. Greywater does not include flow from a toilet or urinal.

(a) "Light greywater" means flows from bathtubs, showers, bathroom sinks, washing machines, and laundry-utility sinks.

(b) "Dark greywater" means flows from dishwashers, kitchen and nonlaundry utility sinks alone or in combination with light greywater.

(5) "Greywater irrigation system" or "system" means an integrated system of components located on the property it serves, or on nearby property where it is legally allowed to be used, that conveys greywater from the residence or other building where it originates and provides subsurface irrigation of plants during the growing season.

(6) "Growing season" means the period of time between the last frost of spring and the first frost of autumn, when annual plants die and biennials and perennials cease active growth and become dormant. The growing season may be extended with the use of a greenhouse so long as the plants irrigated within the greenhouse continue active growth.

(7) "Large on-site sewage system" means an on-site sewage system with design flows of between three thousand five hundred gallons per day and one hundred thousand gallons per day.

(8) "Local board of health" means a board created under chapter 70.05, 70.08, or 70.46 RCW.

(9) "Local health officer" means the person appointed under chapter 70.05 RCW as the health officer for the local health department, or appointed under chapter 70.08 RCW as the director of public health of a combined city-county health department, or a representative authorized by and under the direct supervision of the local health officer.

(10) "Mulch" means a protective covering for establishing a vegetative landscape that is spread or left on the ground to reduce evaporation, maintain even soil temperature, reduce erosion, control weeds, or enrich the soil.

(11) "Nonresidential building" means a building that is used for commercial or other nonresidential purposes.

(12) "On-site sewage system" means an integrated system of components located on or nearby the property it serves that conveys, stores, treats, and/or provides subsurface soil treatment and dispersal of sewage. It consists of a collection system, a treatment component or treatment sequence, and a soil dispersal component. An on-site sewage system also refers to a holding tank sewage system or other sewage system that does not have a soil dispersal component.

(13) "Plant factor" means a number which represents the approximate portion of evapotranspiration used by a plant species.

(14) "Pressure distribution" means a system of small diameter pipes equally distributing greywater.

(15) "Proprietary treatment product" means a greywater treatment technology, method, or material, subject to a patent or trademark that functions to treat greywater generated by residential or nonresidential buildings.

(16) "Public sewer system" means all facilities used in the collection, transmission, storage, treatment, or discharge of any waterborne waste, whether domestic in origin or a combination of domestic, commercial, or industrial wastewater. A public sewer system may also be known as a sanitary sewer system.

(17) "Qualified professional" means an on-site sewage treatment system designer licensed under chapter 18.210 RCW or a professional engineer licensed under chapter 18.43 RCW who is knowledgeable in irrigation system design.

(18) "Residential building" means a building used as a residence including single-family residences and multi-family residences.

(19) "Restrictive layer" means a stratum impeding the vertical movement of water, air, and growth of plant roots, such as hardpan, claypan, fragipan, caliche, some compacted soils, bedrock and unstructured clay soils.

(20) "Single-family residence" means one single-family house that is not used for commercial or other nonresidential purposes.

(21) "Subsurface irrigation" means applying greywater below the surface of the ground directly into the plant root zone.

(22) "Suitable soil" means unsaturated soil above the seasonally high water table and any restrictive layer in which the movement of water, air, and growth of roots is sustained to support healthy plant life and conserve moisture.

(23) "Tier 1 greywater irrigation system" means a light greywater irrigation system with maximum design flows of sixty gallons per day serving a single-family residence. A Tier 1 system serves a single-family residence connected to an approved public sewer system or on-site sewage system.

(24) "Tier 2 greywater irrigation system" means a light greywater irrigation system serving a residential or nonresidential building. A Tier 2 system only serves a building connected to an approved public sewer system or large on-site sewage system, except as provided in WAC 246-274-200 (1)(e).

(25) "Tier 3 greywater irrigation system" means a light or dark greywater irrigation system serving a residential or nonresidential building and using a treatment component. A Tier 3 system only serves a building connected to an approved public sewer system or large on-site sewage system, except as provided in WAC 246-274-300 (3)(e).

(26) "Treatment component" means a technology that treats greywater according to WAC 246-274-400 in preparation for subsurface irrigation of plants.

(27) "Vector" means an animal including, but not limited to, an insect, a rodent, or a bird, which is capable of transmitting an infectious disease from one organism to another.