(1) The following conditions and restrictions apply to each Tier 1 greywater irrigation system:

(a) The greywater must be light greywater.

(b) The total flow of greywater must be sixty gallons per day or less.

(c) The greywater must originate from a single-family residence.

(d) The single-family residence must be served by an approved public sewer system or on-site sewage system.

(e) The greywater must be diverted to the subsurface irrigation system through a single diversion point. Flows from fixtures located close enough to each other to be diverted through a single diversion point may be combined.

(f) The greywater must be delivered through the irrigation system by gravity distribution. Pumps may not be used to convey the greywater.

(g) The greywater may not be stored.

(h) The total minimum irrigation area available to receive the greywater must be adequate based on a calculation of:

(i) The estimated volume of greywater;

(ii) The evapotranspiration rate in inches per week for the geographic area of the state where the landscape or garden is located; and

(iii) The water requirements of the plants, known as a plant factor. A "Greywater System Checklist and Irrigation Area Estimation Tool" is available from the Washington state department of health's website.

(i) The greywater must be distributed throughout the irrigation area.

(j) The homeowner may direct greywater to separate irrigation fields so long as the total flow of greywater to all fields combined does not exceed sixty gallons per day.

(k) The Tier 1 system must be covered by at least four inches of appropriate material which may include suitable soil or other material such as mulch, humus, or compost. If material other than suitable soil is used, the irrigation field cover must be augmented periodically as needed to maintain adequate cover during the growing season.

(l) The homeowner shall ensure that the Tier 1 system is properly operated and maintained.

(m) The homeowner shall maintain a record of the Tier 1 system that:

(i) Shows the location of the system;

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

(iii) Describes the system design and how it meets the requirements of WAC 246-274-100;

(iv) Describes the system's maintenance requirements; and

(v) Includes the calculation of the total minimum irrigation area required under subsection (h) of this section.

(n) The homeowner shall maintain the record of the system on a completed "Greywater System Checklist and Irrigation Area Estimation Tool."

(2) A homeowner may install and use a maximum of two separate Tier 1 systems, with combined flows of one hundred twenty gallons per day or less, to allow for reuse of greywater originating from two separate diversion points. The total flow of greywater to the irrigation field or fields used by each system must not exceed sixty gallons per day.

(3) The local health officer may require the homeowner to register the Tier 1 greywater system(s) by filing the record, required in subsection (1)(m) of this section, with the local health jurisdiction. He or she may require additional review when two separate systems are installed or if the property is served by an on-site sewage system with design flows of less than three thousand five hundred gallons per day.

(4) The owner shall comply with any more stringent regulations adopted by the local health jurisdiction including design and permitting requirements.