Testing Gas Lines With Compressed Air?
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  1. #1
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    Default Testing Gas Lines With Compressed Air?

    I'm about finished with getting some new natural gas lines installed and got to thinking...could I hook my air compressor up to the system to check for leaks? And if so, what pressure should they be filled to?

    That would be really nice since right now my gas service is turned off. (Has been since I bought the building) There is so much gas line, I'm thinking its going to cost a bit of money just to fill the pipes, and if I have to empty them to fix any leaks, that's gonna be wasted money...

    Thanks so much!

    Eric

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    I don't see why that wouldn't work. I would do 125 psi and get out your squirt bottle of soapy water. I have met a few older guys that just used a match to find propane leaks! It works great but you wonder what could happen... Another thought, what about that UV dye you put in the A/C system of a car to find a leak? With all of these it would be key to keep the lines dry.

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    Could you also inject some kind of an odorant into the system before you pressure it up? At least if you can smell something, it gives you much more incentive to go diligently at it with soap and water

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    There is a code that calls for checking of all plumbing lines with pressure. Even drain lines have to be plugged and pressure check, the amount of pressure depends on the application, drains, water, gas each different. Just the soapy water sprayed on each joint.

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    I think some localities require it. The gas pressure is low, on the order of 10 psi (usually measured in inches of water). I think I'd go 30-40psi to fill, troubleshoot each joint until you're satisfied, then valve it off and see what the reading is the next day.

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    The way the gas company checks is to attach a pressure gauge, pressurize, shut off the pressure supply, and watch the gage. If the gage goes down at all, then I'd use a higher pressure and soapy water on all the joints till I found the culprit.

    Jim

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    Someone once told that there is a reason Why the codes specifies a certain pressure.
    Too much pressure can "possibly" stress a joint and actually force a very small leak to seal. Similar in principle to how you need a minumum pressure to seal a check valve.

    Therefore, testing it at a higher pressure than the test specifies is not considered "valid"

    I don't know how acurate this line of thinking is. But there exists a code requirement for pressure testing.

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    Around here, lines are pressurized to 30 psi using a sort of Schraeder valve/pressure meter combo. If it drops at all over 24 hours, it's time to look for leaks.

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    Default Leaks

    We use the same test procedure at they apparently use in California.
    When the inspector comes the next day the pressure must be the same or now the trouble starts.
    wak

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    National Fuel Gas Code specifies 3 times the working pressure- 7"wc for natural gas and 11" wc for propane. 1.2 psi is an acceptable test pressure. Higher pressures are ok and will help find the leak faster. Only piping should be tested. Gas valves, regulators , and meters should be valved off or damage could occur. I use a bicycle pump for residential systems and a small compressor for larger systems. I use a one hour test at 10psi without the needle moving on the pressure gage. Utility requires a signed pressure test certificate before installing meter.

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    I just had a gas line installed and the plumber checked the house lines with 15psi over the course of an hour.

    I think the utility company checked it for less time than that.

    Worked at a code shop with big pressure vessels and they used 5 psi to check for leaks before filling it with water for the real test.

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    In California and many other jurisdictions, the PSI is 15 and they want your word that it has been up for 24 hours. Every inspection I've stood in the last 20 or so years, (hundreds) the inspector lets a little air out, notes the new pressure then wanders around for a little while. It better still be there when he comes back. There is such a thing as a stuck needle.

    I always pump mine to 18PSI the day before. If it's still above 15 a day later, I feel pretty good about the gas company's 1PSI or less gas pressure.

    This is one of the few things that is regulated by the individual providers and not spec'd in the Uniform Building Code, adopted in most the land.

    Bob

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    Thanks for the input!!! No zoning here, so if there's any requirement for testing, its what the gas company would want. Probabley would have been nice to know exactally what they would want, but when I talked to the gas company they were pretty difficult to get info out of...

    So looks like I'm gonna give it a shot at putting compressed air in it, and see what it does! I sure hope it doesn't leak, this is my first shot at gas line work...used lots of teflon thread sealent, and made the joints as tight as I could get them...

    Thanks again!

    Eric

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    Default Teflon OH NO!

    I do so hope that you did not use any of the teflon tape on any of those joints. There is a pipe dope that is specifically used for fuel gas lines. It may contain teflon as an ingredient, but the use of tape on fuel gas lines is a definate No-No. I have seen it used on water lines both with and without pipe dope, but never on any gas or compressed air lines in any building that I have had the privilage of overseeing the installation of sprinkler lines in. It prevents the joint from sealing properly and allows for the gas to work its way through the threads. Pipe dope fills the spaces in the joint and solidifies preventing permiation of the gas. Same goes for compressed air lines since air is a gas. If you did and the Gas Company inspector see it then you will not get your gas turned on.

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    Default gas line

    Yep, still got some of that soft seal left form the last gas line i installed.15 psi for 24 hour's ,no drop in pressure.

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    I'm really surprised at the replies, here. In SW PA, I have installed quite a few gas lines and full service inside the houses, and requirement was 100 PSI, inside and out.

    Outside may be any pressure of supplied gas, meter and regulator will give you, inside, about 1/2 PSI or less, but still must pass 100 PSI test.

    Required test guage was not a dial type bourdon guage, but a Kohlman guage, 15" columnar water column type guage. Valves on it to measure PSI and other combo of valves to measure inches of water.

    Pumping a line with a bicycle pump will wear you out. If you have a compressor available, use it. Took me about 4 hours, one time, TO pressurize 1200 feet of 2" line, with a tankless, oilless compressor. I might still be there, 20 years later, had I used a bicycle pump.

    Calculate the volumn of the line and see how much you have to fill. You will be awed at the volumn of 100 feet or so of even 1" line. If you have spent 10 minutes or so filling a bike tire, and extrapolate, you might be there for quite some time, stroking that plunger.

    Cheers,

    George

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    They do make a natural gas grade teflon tape. I believe it is yellow in color. I've used it and had no problems with inspectors in Ohio, Colorado, and California.

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    do so hope that you did not use any of the teflon tape on any of those joints.
    Okay, I'm sick... The entire gas line I put in has the regular teflon tape on it!!!! And today I just got it all finished up!

    Okay, this is gonna be a big job to redo the entrie line, it goes through very hard to get to places...20 feet in the air, then 24" crawl spaces...

    Please tell me there is a glimar of hope that I can leave it the way it is if it doesn't leak...I see from a quick search on the internet someone says the regular teflon is a no-no due to pieces of it getting cut when the pipes are screwed together...so if I do a leak test and its okay, then purge the lines with compressed air to remove any residue, one would think that would work?

    Thanks!
    Eric

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    I just found the gas companies installation requirements, a little after the fact... Anyway, for thread sealent it says-

    "Where threaded connections are made on above groundpiping, a sealent approved for natural gas shall be applied according to the manufacturer's instructions"

  20. #20
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    Default teflon tape

    I have worked for a natural gas company for over twenty five years and I am sure that the regular white teflon has been used plenty of times on higher pressure gas services than are being discussed here (0-900psi). I would advise you to air the system up as previously instructed and see what happens.


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