246-272A-0230  <<  246-272A-0232 >>   246-272A-0234

Design requirements—Septic tank sizing.

Septic tanks shall:
(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, Required Minimum Liquid Volumes of Septic Tanks:
TABLE VII
Required Minimum Liquid Volumes of Septic Tanks
Number of Bedrooms
Required Minimum
Liquid Tank Volume in Gallons
≤3
900
4
1000
Each additional bedroom
250
(b) For OSS treating sewage from a residential source, other than one single-family residence, two hundred fifty gallons per bedroom with a minimum of one thousand gallons;
(c) For OSS treating sewage from a nonresidential source, three times the design flow.
[Statutory Authority: RCW 43.20.050. WSR 05-15-119, § 246-272A-0232, filed 7/18/05, effective 7/1/07.]
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