An internal hydrostatic or air pressure test shall be made of every section of sewer, including service connections, after the completion of the final trench backfill as follows.
(A) Hydrostatic testing. All pipe and joints in the system shall sustain a maximum leakage limit of 0.3 gallon per hour (gph) per inch diameter per 100 feet when field tested by exfiltration methods. The hydrostatic head for test purposes shall exceed the maximum estimated groundwater level in the section being tested by at least 12 inches, and in no case shall be less than 24 inches above the inside top of the highest section of pipe in the test sections, including service connections. In every case, the height of the water table at the time of the test shall be determined by exploratory holes or such other methods as approved. The length of pipe tested hydrostatically shall be limited so that the pressure on the invert of the lower end of the section shall not exceed 16 feet of water column. The section of pipe to be tested may be filled 24 hours prior to time of hydrostatic testing, if desired, to permit normal absorption into the pipe walls to take place.
(3) All service connection footage included in the test section and subjected to the minimum head specified shall be taken into account in computing allowable leakage. An allowance of 0.2 gph per foot of head above invert shall be made for each manhole included in a test section.
(B) Air testing.
(1) Pipe and joints being air-tested shall be considered acceptable when tested at an average pressure of 3.0 pounds per square inch greater than the average back pressure of any groundwater that may submerge the pipe, when the total rate of air loss from the section being tested does not exceed 2.0 cubic feet per minute; or the section of line does not lose air at a rate greater than 0.0030 cubic foot per minute per square foot of internal pipe surface.
(2) The pipe and joints shall also be considered as acceptable when the time required in seconds for the pressure to decrease from 3.5 to 2.5 pounds per square inch greater than the average back pressure of any groundwater that may submerge the pipe is not less than that computed in accordance with the recommended procedure for conducting acceptance test in the standard details on file in the city office.
(C) Manholes.
(1) A random sample of manholes selected by the secretary up to 10% of the total project number, but in no case less than 5%, shall be tested by hydrostatic methods. Leakage in each manhole shall not exceed that specified for hydrostatic testing.
(2) If more than 50% of the manholes tested fail the hydrostatic test, the contractor shall be required to test all or as many manholes as the secretary may deem necessary. All manholes that do not meet the requirements of the test, or are unsatisfactory from visual inspection, shall be repaired to conform to the requirements herein.
(Ord. 46, passed 4-8-1975)