DEVELOPMENT STANDARDS SECTION 2 – SEWER STANDARDS 9 T E S T I N G O F G R A V I T Y S E W E R S Method of testing gravity sewers and manholes shall be as follows: Testing shall be as specified in the most current version of Section 7-17.3 of the WSDOT Standard Specifications. The following requirements for Sewer testing is from the 2016 Standard Specifications. 2016 WSDOT Standard Specifications (or most current) 7-17.3(2) Cleaning and Testing 7-17.3(2)A General Sewers and appurtenances, where required in the Plans, shall be cleaned and tested after backfilling by either the exfiltration or low pressure air method at the option of the Contractor, except where the ground water table is such that the Engineer may require the infiltration test. All work involved in cleaning and testing sewer lines between manholes or rodding inlets as required shall be completed within 15 working days after backfilling of sewer lines and structures. Any further delay will require the written consent of the Engineer. The Contractor shall furnish all labor, materials, tools, and equipment necessary to make the test, clean the lines, and perform all incidental work. The Contractor shall perform the tests under the direction and in the presence of the Engineer. Precautions shall be taken to prevent joints from drawing during tests, and any damage resulting from these tests shall be repaired by the Contractor at no expense to the Contracting Agency. The manner and time of testing shall be subject to approval by the Engineer. All wyes, tees, and stubs shall be plugged with flexible jointed caps, or acceptable alternate, securely fastened to withstand the internal test pressure. Such plugs or caps shall be readily removable, and their removal shall provide a socket suitable for making a flexible jointed lateral connection or extension. Testing side sanitary sewers shall be for their entire length from the public sewer in the street to the connection with the building’s plumbing. Their testing shall be as required by the local sanitary agency but in no case shall it be less thorough than that of filling the pipe with water before backfilling and visually inspecting the exterior for leakage. The decision of the Engineer as to acceptance of the side sanitary sewer shall be final. If any sewer installation fails to meet the requirements of the test method used, the Contractor shall determine, at no expense to the Contracting Agency, the source or sources of leakage and shall repair or replace all defective materials or workmanship at no expense to the Contracting Agency. The complete pipe installation shall meet the requirements of the test method used before being considered acceptable. 7-17.3(2)B Exfiltration Test Prior to making exfiltration leakage tests, the Contractor may fill the pipe with clear water to permit normal absorption into the pipe walls provided, however, that after so filling the pipe, the Contractor shall complete the leakage test within 24 hours after filling. When under test, the allowable leakage shall be limited according to the provisions that follow. Specified allowances assume pre-wetted pipe. Leakage shall be no more than 0.28 gph per inch diameter per 100 feet of sewer, with a hydrostatic head of 6 feet above the crown at the upper end of the test section, or above the natural ground water table at the time of test, whichever is higher. The length of pipe tested shall be limited so that the pressure at the lower end of the Section tested does not exceed 16 feet of head above the invert, and in no case shall be greater than 700 feet or the distance between manholes when greater than 700 feet. Where the test head is other than 6 feet, the maximum leakage shall not exceed the amount determined from the following equation: Maximum leakage (in gallons per hour) = 0.28 x (√H/√6) x D x (L/100) Where: D = diameter (in.) L = length of pipe (ft.) H = test head (ft.) 7-17.3(2)C Infiltration Test Where the natural ground water head over the pipe is 2 feet or less above the crown of pipe at the upper end of the test section, the infiltration test leakage shall not exceed 0.16 gallons per hour per inch of diameter per 100 feet of pipe length. The length of pipe tested shall not exceed 700 feet or the distance between manholes when greater than 700 feet. Where the natural ground water head is greater than 2 feet, the maximum leakage shall not exceed 0.16 gallons per hour per inch of diameter per 100 feet of pipe length times the square root of the natural ground water head. The leakage can be determined from the equation: Maximum leakage (in gallons per hour) = 0.16 x (√H√2) x D x (L/100) Where: D = diameter (in.) L = length of pipe (ft.) H = natural ground water head (ft.) When a suitable head of ground water exists above the crown of the pipe and when the pipe is large enough to work inside, acceptance may be based on the repair of visible leakage by means satisfactory to the Engineer. 7-17.3(2)D Other Test Allowances For either the infiltration or exfiltration test, all lateral or side sewer branches included in the test section shall be taken into account in computing allowable leakage. An allowance of 0.2 gallons per hour per foot of head above invert shall be made for each manhole included in a test section. Upon final acceptance of the work all sewers, side sewers and fittings shall be open, clean, and free draining.
