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  1. #1
    Join Date
    Dec 2006
    Location
    toronto, canada
    Posts
    551

    pipe dope trigger electric gas leak detector

    Repair some gas leaks, check again, alarm, put on soap, nothing. Put tip of detector close to dope can, alarm again. Use inficon and yellow jacket's detector try all dopes at supply, same thing. How about you guys? Any suggestion? Thanks.

  2. #2
    Join Date
    Feb 2005
    Location
    small island in the Pacific Ocean
    Posts
    558
    same problem. almost drove me insane one day. quit using natural gas detector and stuck with soap. sorry no suggestions, hopefully someone else does

  3. #3
    Join Date
    Jun 2004
    Posts
    956
    we use the electronic to get us in the area and prove with soap, just too sensitive

  4. #4
    Join Date
    Jun 2000
    Location
    WYO
    Posts
    2,019
    Clean excess dope and let dry for a day
    never say never

  5. #5
    Join Date
    Jan 2006
    Location
    Hangin out with you losers
    Posts
    1,043
    use thread tape
    I remember my first day,It was fun!

  6. #6
    Join Date
    Dec 2006
    Location
    Moorhead Minnesota
    Posts
    24
    Quote Originally Posted by vibration View Post
    Repair some gas leaks, check again, alarm, put on soap, nothing. Put tip of detector close to dope can, alarm again. Use inficon and yellow jacket's detector try all dopes at supply, same thing. How about you guys? Any suggestion? Thanks.
    Yep, same problem here. Doesn't mater what brand detector you are using. The pipe dope is a petroleum product. This is why the detector is going off. This is what I was told by a factory rep. After that new pipe dope cures for awhile. It will stop setting the detector off. Of course this doesn't help us when we are there tring to find leaks.

  7. #7
    Join Date
    Jul 2007
    Location
    NW PA
    Posts
    75
    Quote Originally Posted by scottsacavsfan View Post
    use thread tape


    when i was in Ohio thread tape was not allowed by code ...plumbing thread tape has teffon and gas dries tape and shrinks then now seal....i have seen thread tape thats suppose to be for gas (yellow) @ home depot but have never used prob wont stick will with dope and bubbles



    Bob

  8. #8
    Join Date
    Aug 2004
    Location
    S.E. Pa
    Posts
    6,294

    Cool gas leak detection

    Since all pipe dopes are hydrocarbon based, your garden store variety sniffer will hit on it as a false positive. In Northern Va., the building officials test with a Bacharach Leakator 10 set to one tick per second. If it rises any amt. at all, they Red Tag it. The appliance installer must come behind them with Bacharach Gas Pointers, which have sensors specific to one gas. You buy one machine for NG and another for LP--very expensive. If they don't pick up a leak, then the Red Tag is lifted.

    Do not use Teflon (PTFE) tape. Strands of it can come loose, get blown into gas valves and cause fires and explosions. While it is allowed by the gas codes, it has a higher potential for problems. Always leave the first two threads bare.

    Do not use regular soaps for bubble testing for leaks. The chloride ions have been proven to cause stress cracking and leaks. Use only commercially prepared non-corrosive solutions.

    Everything leaks--it just a question of how much is acceptable. While a homeowner may sense a leak in the 1-10 ppm range using their nose, the LEL for LP gas is 21,500 ppm and NG is ~40,000 ppm. Since humans can detect mercaptans in the range of as low as 0.5 parts per Billion, you might get a trace leak where one molecule flew up their nose and they smelled "gas". Not everyone is sensitive to the odorants and various compounds are used. There is rising evidence that "odor fade" is much more widespread than first thought. Recent gas explosions in Texas has uncovered failing riser compression fittings where the wet clay soild filtered out the mercaptan and things went bad.


    You can get false positives from those sniffers from a variety of substances including silicone caulk, soap test solutions, wet insulation, oily sheetmetal, greasy handprints, off gasing paints, and aldehydes as with CO poisoning, so have your CO analyzer running, too. I use a Sharpie pen to demonstrate this to homeowners. the toluene hits.

    If you hold a sniffer near a gas regulator when the pressure changes such as when a burner lights or shuts off, you can get a one time burp/ fart at the vent on the regulator as it equalizes. A sustained leak means the diaphragm has ruptured and the entire valve proably should be replaced. Common with high test pressures when the appliance is not isolated and capped per the codes and listing. Any testing above 14 wci requires the appliance be isolated and capped. Also, these high pressure tests are assinine and don't prove a dang thing. A high pressure gauge can miss low level leaks, too.
    HTH
    Hearthman

  9. #9
    Join Date
    Jan 2006
    Location
    Hangin out with you losers
    Posts
    1,043
    Quote Originally Posted by rjw_hvac_tech View Post
    when i was in Ohio thread tape was not allowed by code ...plumbing thread tape has teffon and gas dries tape and shrinks then now seal....i have seen thread tape thats suppose to be for gas (yellow) @ home depot but have never used prob wont stick will with dope and bubbles



    Bob
    I was just being a smartA$$ I never used tape either
    I think you have to wait for the stuff to dry to get a accurate reading
    I bought the informant and it does a great job of sampeling then retesting the same fitting to "check" its self.
    I remember my first day,It was fun!

  10. #10
    Join Date
    Jun 2007
    Location
    Rogers,MN
    Posts
    22
    I used yo work for natural gas utility-decaying leaves,lawn fertalizer,pipe dope,etc set it off-and then customer gets all upset thinking they should run for their lives.Good old soap bubbles work the best.If you have a lot of concealed piping you cannot soap--you can extinguish all pilots until safety trips,then spot the gas meter for movement,Or you can again turn off all pilots,put a u-tube manometer on a pressure tap somewhere,and turn off gas meter(or l.p. tank.Should see no decrease in pressure.These are great ways to prove to a customer(and yourself) that there is a leak in piping,whether it be underground in that line to grill or garage,buried in ceiling,or whatever.

  11. #11
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,915
    Use Rectorseal T-plus-2 teflon enriched sealant, it won't set off gas leak detectors, and unlike most pipe dope, can be used on threaded drain pan connections to plastic and PVC drain pans in cooling coils.

    The T-plus-2 also has a long shelf life, and won't separate in the can like regular pipe dope does.
    Last edited by mark beiser; 07-29-2007 at 12:43 PM.
    If more government is the answer, then it's a really stupid question.

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