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    pbmendez's Avatar
    pbmendez Posts: 2, Reputation: 1
    New Member
     
    #1

    Jul 3, 2009, 07:19 PM
    Can't find leak in Gas Pipes
    We are renovating a home, our plumber took our existing gas lines, we moved where the stove was and removed an old bathroom heater. The rest of the lines stayed intact.
    From the meter comes a long run to the furnace in the attic, then splits to the stove and hot water tanks.

    All pipe is existing except the new run to move the stove from one side of the kitchen to the other.

    Our gas is off.

    Our plumber started with pressure at 50lbs - and then used the soapy water to test all connections. There were two old shut off connections, one at the hot water tank and one at the furnace that were bad, we changed those. We repressurized the system and in 2 days it was down to 0

    Next weekend - re-charged and resoaped everything, couldn't find anything (so we removed the old bathroom heater) - it was previously left connected but thought this was probably the problem so we disconnected it.

    Re-charged the system to 90#'s - resoaped everything - no bubbles. Held 90#'s for 2 hours or so, then dropped to 60 in 6 hrs, it was below 30 by morning and 0 by the end of the 2nd day.

    We had a friend who used a stethescope kind of device to see if he could hear the leak. No luck.

    Gauge is fine, we switched that out all three times.

    How else can we find the leak? Someone mentioned a dye you can charge in the pipes and use a black light to see where the particles are escaping the pipe from. Said its used in automotive AC, I can't find anywhere that it is used for house gas and don't want to do something stupid.

    Any ideas would be greatly appreciated. We have friends staying there and our plumber can only work on it on the weekends. They have yet to have a warm shower.

    Please help
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
    Uber Member
     
    #2

    Jul 4, 2009, 12:40 AM

    This should help:

    How to Identify & Correct LP Gas or Natural Gas Leaks in gas piping, at controls, valves, connections, and appliances
    speedball1's Avatar
    speedball1 Posts: 29,301, Reputation: 1939
    Eternal Plumber
     
    #3

    Jul 4, 2009, 05:27 AM
    Try again with the soapy water.. The gas is escaping for some where. Have you checked the burners on the furnace and water heater to be sure you're not losing pressure past the shutoffs? Let me know what you find. Tom
    iamgrowler's Avatar
    iamgrowler Posts: 1,421, Reputation: 110
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    #4

    Jul 4, 2009, 06:51 AM
    Quote Originally Posted by pbmendez View Post
    Our plumber started with pressure at 50lbs - and then used the soapy water to test all connections. There were two old shut off connections, one at the hot water tank and one at the furnace that were bad, we changed those. We repressurized the system and in 2 days it was down to 0
    50lbs is too much -- And 90lbs is way too much.

    If we're talking natural gas and not LP (propane) You should be testing somewhere between 8 and 15psi.

    Most of the gas cocks carried by the big box stores are rated for 30psi maximum.

    Also, you mention that the gas is off, but you don't specify if the gas is disconnected and capped at the meter -- It should be -- And hopefully your Plumber didn't blow apart the diaphragm in the regulator at the meter by pumping it up in excess of 30psi.

    For a proper gas piping test: All appliances should be disconnected and capped/plugged after the gas cock with the gas cock opened and the meter should be disconnected and capped or plugged on your side of the meter, not the utilities.

    Pressurizing should be done at 8psi with a 15lb gauge or 15psi with a 30lb gauge -- A gauge higher than 30lbs should not be used.

    If the piping will hold 8 or 15psi for two hours with no pressure drop, then the piping meets testing specs.
    Milo Dolezal's Avatar
    Milo Dolezal Posts: 7,190, Reputation: 523
    Plumbing Expert
     
    #5

    Jul 4, 2009, 07:17 AM

    Did you remove shut off valves at the appliances completely and plugged it with 1/2" galvanized plug ?
    pbmendez's Avatar
    pbmendez Posts: 2, Reputation: 1
    New Member
     
    #6

    Jul 4, 2009, 08:04 AM
    Quote Originally Posted by Milo Dolezal View Post
    Did you remove shut off valves at the appliances completely and plugged it with 1/2" galvanized plug ?
    Yes he did remove all appliances and he capped the connection to the meter so it wouldn't damage the meter. We will try the solutions suggested. Thanks to all.
    Milo Dolezal's Avatar
    Milo Dolezal Posts: 7,190, Reputation: 523
    Plumbing Expert
     
    #7

    Jul 4, 2009, 08:10 AM

    If you pressurize it - let's say - to 50 psi, or higher, the escaping air will actually be audible and traceable by ear. But you want to do this when noise pollution is down, like on Sunday eve.

    Also, don't forget to cap off ALL appliances - like furnace under the house, A/C in the attic, wall heater, BBQ on side of the house, Fire Pit, Pool heater, etc...

    As far as pool, bbq and fire pit goes, pipes and the leak may be under ground. Here, you would have to disconnect it and cap it off before pipes enter ground...
    massplumber2008's Avatar
    massplumber2008 Posts: 12,782, Reputation: 1210
    Senior Plumbing Expert
     
    #8

    Jul 4, 2009, 08:18 AM
    Make sure the plumber checks his own test apparatus. I have seen leaks develop at the testing equipment and go undetected for hours... ;)

    A proper test setup will include the shrader valve, a proper test gauge and a shutoff. Test all, and shutoff the shutoff at the test point. Open shutoff 10 minutes later... if pressure falls then leak is in system. If not, the elak may be at the test apparatus.

    MARK

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