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  1. #1
    Join Date
    Nov 2011
    Location
    St. Louis
    Posts
    3,427

    Natural Gas Leaks

    I'm sure there must be threads in this forum regarding natural gas leaks in residentials, but I always get a ton of unrelated material when I use the search engine. The info on the net in genral is all over the map - folks telling people on yahoo to dump ungodly amounts of PSI into their lines etc...

    I'm interested in what steps and methods everyone else is using for gas leak calls when the meter has been locked out. Manometer, soap bubbles and your own breath? Introduce a combustible gas and electronic detector? Common leakage points? Best access for manometer (outside meter, drip leg)?

    Tips and cautions? If you introduce propane for testing purposes, what type of rig do you use and do you simply watch the manometer to avoid too much pressure?

    How many inches of WC does your local gas company insist on seeing and for how long?

    Maybe there already many threads covering this and someone could just point the way for me?

    Many thanks as always,

    h

  2. #2
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,060
    Quote Originally Posted by hurtinhvac View Post
    I'm sure there must be threads in this forum regarding natural gas leaks in residentials, but I always get a ton of unrelated material when I use the search engine. The info on the net in genral is all over the map - folks telling people on yahoo to dump ungodly amounts of PSI into their lines etc...

    I'm interested in what steps and methods everyone else is using for gas leak calls when the meter has been locked out. Manometer, soap bubbles and your own breath? Introduce a combustible gas and electronic detector? Common leakage points? Best access for manometer (outside meter, drip leg)?

    Tips and cautions? If you introduce propane for testing purposes, what type of rig do you use and do you simply watch the manometer to avoid too much pressure?

    How many inches of WC does your local gas company insist on seeing and for how long?

    Maybe there already many threads covering this and someone could just point the way for me?

    Many thanks as always,

    h
    Isolate all gas valves from all appliances, water heater, stove, furnace, boiler and meter. Pressure test with nitrogen through any sediment trap, 5 pounds is plenty and soap all joints.

    look at IFGC section 406 through 406.7.4

  3. #3
    new to site, switched trades, just learning the hvac trade, already have some exp... Anyway , for your question, i would remove all valves from your appliances, and cap the line, then an air test 30 psi /30 min,check your gauge, if pressure drops, re-pressurize, then soap all joints.

  4. #4
    wheir i live, gas co supplies 2 pounds before reg and 7-11 w.c after

  5. #5
    Join Date
    Nov 2011
    Location
    St. Louis
    Posts
    3,427
    Quote Originally Posted by rooki View Post
    wheir i live, gas co supplies 2 pounds before reg and 7-11 w.c after
    Same here. So why 30 psi pressure test?

    Would you not blow right thru gas cocks rated at 1/2 psi (14" wc)?

    Even 5 psi seems like you would be asking to create brand new leaks?

  6. #6
    Join Date
    Feb 2004
    Posts
    2,458
    Quote Originally Posted by rooki View Post
    wheir i live, gas co supplies 2 pounds before reg and 7-11 w.c after
    Are you about that

  7. #7
    Join Date
    Feb 2012
    Location
    South Georgia
    Posts
    105
    According to the ICC 406.4.1 "the test pressure to be used shall not be less than 1 1/2 time the proposed maximum working pressure, but not less than 3 psig." and continues later on to say that less than 10 cu. ft. piping capacity is tested for ten minutes... for what its worth.

  8. #8
    Join Date
    Feb 2012
    Location
    South Georgia
    Posts
    105
    section 406 in the ICC is all bout testing and purging gas piping, types of testing gasses, pressures, time tables, etc..

  9. #9
    Quote Originally Posted by hurtinhvac View Post
    Same here. So why 30 psi pressure test?

    Would you not blow right thru gas cocks rated at 1/2 psi (14" wc)?

    Even 5 psi seems like you would be asking to create brand new leaks?
    especially the older valves the ones that were packed with grease err whatever they used they will definately start leaking with that kind of presure...(yes I learned this the hard way) I only use 1 psi now to test the system but I will be investing soon in a way to check in w.c. so I can more accuratly measure around 1/2 psi

  10. #10
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    Quote Originally Posted by RobFarns View Post
    especially the older valves the ones that were packed with grease err whatever they used they will definately start leaking with that kind of presure...(yes I learned this the hard way) I only use 1 psi now to test the system but I will be investing soon in a way to check in w.c. so I can more accuratly measure around 1/2 psi
    he said to remove all gas cocks and cap the pipe. Never used 30 PSI my self when five pounds would do.

  11. #11
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,060
    Quote Originally Posted by hurtinhvac View Post
    Same here. So why 30 psi pressure test?

    Would you not blow right thru gas cocks rated at 1/2 psi (14" wc)?

    Even 5 psi seems like you would be asking to create brand new leaks?

    Pressure rating on standard gas cocks is 125 psi

    gas valves are rated at 14 inches of water column or 1/2 psi.

  12. #12
    Join Date
    Nov 2011
    Location
    St. Louis
    Posts
    3,427
    Quote Originally Posted by second opinion View Post
    Pressure rating on standard gas cocks is 125 psi

    gas valves are rated at 14 inches of water column or 1/2 psi.
    Can we take a step back and clarify our terms?

    The gas "cock," meaning the individual shut off to the furnace, water heater, clothes dryer stove etc. typically have 1/2 psi stamped on the side.

    Maybe a bit more on some...but 125 PSI???

    125 x 28 " wc... = 3500 " WC

    In a residential setting?

  13. #13
    Join Date
    Jun 2008
    Posts
    112
    I had a helper once that did the gas line at a new house and the customer complained of a gas smell sometimes. So my helper went back meter dial tested nitro tested etc. He finally had enough when he could'nt find the leak so he capped the lines at the units put 90psig into the line to find the leak and well pretty much all the joints leaked. In the end after he redid the joints we put the line back in hooked up to the units. I fired up the units and the leak ended up being on the new gsw water heater on the corrugated main burner line going into the flame guard door the nut was just hand tight from the factory and leaked like crazy.

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