The design engineer shall verify that all sewage tanks used in the LOSS are tested for water tightness by either vacuum testing or water-pressure testing.

1. (1) Vacuum testing steps:

   1. (a) Seal the empty tank;
   2. (b) Temporarily seal access openings, risers, and inlet and outlet pipes; and
   3. (c) Introduce negative pressure into the tank and apply a vacuum to four inches (one hundred millimeters) of mercury.
   4. (d) The tank passes if ninety percent of vacuum is held for two minutes.

2. (2) Water-pressure testing steps:

   1. (a) Seal the empty tank;
   2. (b) Seal access openings, risers, and inlet and outlet pipes;
   3. (c) Fill the tank with water two inches into the riser and let stand for twenty-four hours; and
   4. (d) Add water to the tank, if necessary, to the original level.
   5. (e) The tank passes if the water level is unchanged after one hour.
3. (3) The design engineer shall reject tanks that do not meet the water tightness standard.

4. (4) If the tank fails, the owner may try to repair and retest the tank.

   1. (a) The test must be completed according to the requirements of subsection (2) or (3) of this section.
   2. (b) If the water-pressure test method is used, the twenty-four hour standing time is not required.

[Statutory Authority: RCW 70.118B.020. WSR 11-12-035, § 246-272B-05200, filed 5/25/11, effective 7/1/11.]