WAC 246-272A-0232. Design requirements — Septic tank sizing

Septic tanks must: (1) Have at least two compartments with the first compartment liquid volume equal to one-half to two-thirds of the total liquid volume. This standard may be met by one tank with two compartments or by two single compartment tanks in series. (2) Have the following minimum liquid volumes: (a) For a single-family residence use Table VII: Table VII Required Minimum Liquid Volumes of Septic Tanks Number of Bedrooms Required Minimum Liquid Tank Volume in Gallons ≤4 1,000 Each additional bedroom 250 Number of Bedrooms Required Minimum Liquid Tank Volume in Gallons ≤4 1,000 Each additional bedroom 250 (b) For OSS treating sewage from a residential source, other than one single-family residence, 250 gallons per bedroom with a minimum of 1,000 gallons; (c) For OSS treating sewage from a nonresidential source, three times the design flow. (3) Comply with chapter 246-272C WAC.