Method Statement for Leak Testing of Underground FRP Surface Drain Line

Pre-Testing Activities for Underground FRP Surface Drain Line

• Ensure that all relevant documents and procedures have been approved by OWNER prior to commencement of the work, and that the latest revisions of IFC drawings, specifications including approved procedures are disseminated to concerned personnel who will carry out the work.

• Ensure that the required tools and equipment’s for leak testing such as plumber plug, hose clamp, clear hose, etc. is available.

• Conduct site inspection to check and verify that the gradient, invert elevation and all joints are completely assembled and properly cured. Ensure also that the piping systems have been flushed clean of debris and sand or any foreign objects prior to leak testing. 

• Check and verify that the pipe have been buried to the minimum depth above the top of the pipe as per design requirement prior to water filling the system. Ensure that all joints have been left uncovered to allow inspection during leak testing.

• Prior to leak testing, ensure that the pipe section to be tested have been plugged at the downstream end of the pipe (e.g. at the second manhole).

Testing Activities for Underground FRP Surface Drain Line

• Wherever possible, leak testing shall be carried out from manhole to manhole. Short branch drains connected to a main sewer between manholes shall be tested as one system with the main sewer. Long branches shall be tested separately from manholes and testing shall be conducted in accordance with OWNER Specification. Design and Construction of Sewers and SUBCON Standard Operating Instructions respectively. 

• If the piping system is ready for testing, inject the test medium, potable water at the drain cleanout section of the piping system. The test shall start approximately one hour after filling the pipe with water. Water shall be added to maintain test head to cover water loss due to absorption and air pockets in certain piping configuration. 

• To determine leakage on the system, insert a clear hose ¾” diameter (standpipe) into the nozzle of plumbers’ plug up to the highest level of the water inside the manhole or clean out. Tighten the hose clamp, then fill the hose with water extending up to at least 1.5 meter high above the crown of the pipe at the high end, but not more than 6 meter at the low end. 

• The loss of water over a period of 30 minutes shall be measured by adding water from a measuring vessel at 10-minute intervals and noting the quantity required to maintain the original water level. For this test, the average quantity of water added shall not exceed 1.0 liter per hour per 100 meters linear distance per centimeter of nominal internal drain diameter. 

• Pipe exfiltration (leakage) that causes a drop in the test water level will be apparent by the change in the water level in the standpipe. Any leaks visible during water testing shall be repaired. Defective parts of the drain system shall be removed, replaced, and retested.

• Below is the maximum allowable exfiltration (leakage):

• Storm Sewers  - 0.00018 liters / mm diameter / m / h   

                                    (0.0039 gallons / in diameter / ft / h)

  

• Sanitary Sewers - 0.000037 liters / mm diameter / m / h 

                                      (0.0008 gallons / in diameter / ft / h)

• To rectify the leaking joint or defective parts of the system, remove the plumber’s plug to drain the water out. Rectify immediately the affected leak joint. Cured it properly before leak testing will be carried out again.

• After rectifying the affected joint, fill the system again with potable water and repeat the above-mentioned method, then submit request for inspection to be conducted in accordance with OWNER project specification.

• Once the inspection is completed and accepted by OWNER, drain the test medium. The same methodology shall be applied to the next succeeding loops until the whole piping system is fully tested.

• Upon satisfactory completion of inspection and acceptance by OWNER, final backfilling commences and shall be carried out in accordance with OWNER Specification and SUBCON Standard Operating Instruction respectively.   

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