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Old 02-09-2013, 10:27 PM   #1
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very slow natural gas leak, need advice


I recently had a black iron gas line installed at my house for a gas dryer. The plumber called the permit inspector and he gave the install an ok and then the gas company set the meter. Plumber came back out and took the line loose on the meter and installed a manifold and additional line for a gas heater. Problem is that even prior to installing the additional lines the air gauge hooked to the line would leak down a couple of lbs each day, but it held pressure long enough to pass the permit inspection. I can't get the plumber back out to work on it and have been trying to locate the leak myself. Tried dish soap and water sprayed on, can't find it. Tried pumping up the line to 90 psi and still can't find it. Any suggestions how to locate a really slow leak? Its on my side of the meter. Any advice?

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Old 02-09-2013, 10:52 PM   #2
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very slow natural gas leak, need advice


Call the city? Call a new plumber?

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Old 02-09-2013, 11:46 PM   #3
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Mike I donít know where youíre from but here in Southern CA, we just call the Gas company and they have meter that sniffs out the leak and it a free service although they may turn of the gas if there is a leak until it can be fixed.


my daughter had a leak at her furnace and the gas guy actually fixed it right on the spot for free.
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Old 02-10-2013, 06:29 AM   #4
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very slow natural gas leak, need advice


Its not require to hold X pounds of pressure for days. The gas line will have less the 1/2 pound of pressure in it hen its under normal use.

If you put 90 pounds of pressure in it, and any of the gas shut offs to the appliances were open. you may have damaged them. They are not designed to take more then 1/2 pound of pressure. A gas valve is allowed to leak 200 CCMs an hour.
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Old 02-10-2013, 06:36 AM   #5
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very slow natural gas leak, need advice


leave well enough alone ..plumber and inspector were satisified with test so should you be ..if you put pressure on a line and it sits overnite it will loose pressure due to expanision and contracting due to tempeture change,as mentioned only about 6 ozs of gas pressure in line.... ben sr
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Old 02-10-2013, 09:11 AM   #6
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leave well enough alone ..plumber and inspector were satisified with test so should you be ..if you put pressure on a line and it sits overnite it will loose pressure due to expanision and contracting due to tempeture change,as mentioned only about 6 ozs of gas pressure in line.... ben sr
I understand that the pressure will fluctuate over night with temperature changes, but still seems like it shouldn't leak out at all. The inspectors test is for the 10 minutes while he is on site, in 10 minutes the line will not leak down since it is leaking about 2 lbs a day, after a few days 15 lbs of air pressure in the line will completely leak out. If that was gas leaking couldn't it accumulate in an enclosed area and become an explosion hazard?
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Old 02-10-2013, 09:19 AM   #7
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If that was gas leaking couldn't it accumulate in an enclosed area and become an explosion hazard?
Yes with the proper air/gas ratio and then an ignition source.

If the gas was leaking.

Like suggested, Call gas company and they will sniff it out.
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Old 02-10-2013, 09:21 AM   #8
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If your entire gas line is 1" black pipe, and 100 foot long. At 15 PSIG it had 2.6 cubic foot of air in it. For every .026 cubic foot of air that leaked out, it dropped .15 PSIG. The amount of gas that would like out at 14"(1/2 PSIG) is so little that it would not be enough gas to take a flame, let alone support a continued flame.

You would need atleast 4% gas to air for it to ignite.
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Old 02-10-2013, 09:27 AM   #9
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very slow natural gas leak, need advice


From the Natl Fuel and Gas Code
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Old 02-10-2013, 05:19 PM   #10
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I understand that the pressure will fluctuate over night with temperature changes, but still seems like it shouldn't leak out at all. The inspectors test is for the 10 minutes while he is on site, in 10 minutes the line will not leak down since it is leaking about 2 lbs a day, after a few days 15 lbs of air pressure in the line will completely leak out. If that was gas leaking couldn't it accumulate in an enclosed area and become an explosion hazard?
are you testing back against stops and appliance valves? or are you testing against caps and plugs....what type of gauge are you using ..ben sr
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Old 02-10-2013, 06:19 PM   #11
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very slow natural gas leak, need advice


As it leaked before the work was done, was not apparent to the gas fitters or inspecters testing, was not apparent to your own joint testing,
did you remember to include your tester in the soap test as well.

Just how did you isolate all your appliances and the meter from your pressure test?
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Old 02-10-2013, 06:42 PM   #12
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very slow natural gas leak, need advice


25 years ago a friend and I installed the black iron gas line in the crawspace of my home - 1" mostly - then 3/4" off that going to the future furnace, hot water tank, and dryer. When the gas company tested the line it failed so I took the line apart and put it all back together to the point it ended up an inch or 2 shorter when I got to the end of the run. It passed with no problem when it was retested.
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Old 02-10-2013, 10:09 PM   #13
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very slow natural gas leak, need advice


Nothing has been hooked up to my black iron pipes yet ( no appliances). The meter was set and we disconnected it after it was set to start work on a separate gas line running to the garage which has not been tied into anything yet. So the leak I am looking for is in one of two lines that are tied together near the meter and connected at one end with an air valve and 100 lb pressure gauge and the other ends terminate with ball valves. Thanks
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Old 02-10-2013, 11:14 PM   #14
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very slow natural gas leak, need advice


The lines should terminate with a cap/plug in/on the valves as they can seep a small amount of gas.

It's a good idea to have ball valves on your test assembly: one to isolate the gauge from the pipe and one to isolate the schraeder valve, both of which can leak. Bourdon tube gauges can leak, especially if it's an old one used many times or bounced around in the back of a truck, and soapy water won't necessarily show the leak because it's inside the dial.

Fill the line to 30psig, isolate the test assembly by shutting off the valves on the test assembly. Leave it for a while before checking the gauge. If the pressure has dropped, open the valve and if the pressure rises, your gauge was leaking. On the other hand, if the gauge hasn't dropped, open the shutoff to the line and if it's dropped, you have a piping leak.

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