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new gas line pressure test

rich67 Member Posts: 21
The guys were here installed new gas line from the meter to boiler room. They put a guage on it and pressurized it. In four days it has lost most all the pressure.

So yes there's a leak that needs to be fixed. Is there an allowable loss or can there be none at all?


  • Bob Harper
    Bob Harper Member Posts: 955
    gas pressure testing

    first, refer to my post in the Plumbing section on gas pressure testing.

    A test only has to be 10 min.-not 4 days. However, the code does not state any allowable leakage. In a long term test like this, the leak is often at the test gauge and not the actual piping job. Note that testing at pressures above 1/2psi require the pipe be disconnected from the appliance and capped then tested. Testing above this pressure may blow the diaphragm in the appliance valve or an MP regulator. Do not rely on a gas cock to hold against test pressure.

    If a test lost all pressure over 4 days, I'd be using an electronic gas sniffer to localize the leak then prove it with a non-corrosive  thin-film commercial soap bubble test solution.

  • rich67
    rich67 Member Posts: 21
    edited August 2013
    This is a new installation

    There are no appliances hook up to the line and since there is more than one installation on my street, I think the inspector will come and inspect  them all at the same time. I don't know when that will be. They pressurized it to 15 psi initially. It's dropped down to below 3 psi over the 4 days.

    I just read Mr Harper's post in the plumbing section. It explains it perfectly. 
  • gennady
    gennady Member Posts: 839
    pressure test

    In NYC, gas pressure test must be 3 psi for 30 minutes, for unpainted pipe, and 90 psi for 30 min for painted pipe.

    but in your jurisdiction if 2012 INTERNATIONAL FUEL GAS CODE® accepted:

    406.4 Test pressure measurement. Test pressure shall be measured with a manometer or with a pressure-measuring device designed and calibrated to read, record or indicate a pressure loss caused by leakage during the pressure test period. The source of pressure shall be isolated before the pressure tests are made. Mechanical gauges used to measure test pressures shall have a range such that the highest end of the scale is not greater than five times the test pressure.

    406.4.1 Test pressure. The test pressure to be used shall be no less than 1 ½ times the proposed maximum working pressure, but not less than 3 psig (20 kPa gauge), irrespective of design pressure. Where the test pressure exceeds 125 psig (862 kPa gauge), the test pressure shall not exceed a value that produces a hoop stress in the piping greater than 50 percent of the specified minimum yield strength of the pipe.

    406.4.2 Test duration. Test duration shall be not less than ½ hour for each 500 cubic feet (14 m3) of pipe volume or fraction thereof. When testing a system having a volume less than 10 cubic feet (0.28 m3) or a system in a single-family dwelling, the test duration shall be not less than 10 minutes. The duration of the test shall not be required to exceed 24 hours.

    406.5 Detection of leaks and defects. The piping system shall withstand the test pressure specified without showing any evidence of leakage or other defects.

    Any reduction of test pressures as indicated by pressure gauges shall be deemed to indicate the presence of a leak unless such reduction can be readily attributed to some other cause.
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