Gas Line - Can't Find The Leak

 
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Old 04-19-2007, 01:34 PM   #1
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Gas Line - Can't Find The Leak


We are installing a new run of gas line and are now pressure testing it. We have a leak in the line soaped all the joints and the guage and can't find the leak. We have even removed and redone sections that maybe not installed properly to make sure everything is tight. we have over pressured the line to try and exagerate the leak - no success.

Can't find it. Anyone have any suggestions? We are about to just put gas in it and take a lighter to all the joints. (only kidding) but that is the frustration level we are at this point.
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Old 04-19-2007, 03:11 PM   #2
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Re: Gas Line - Can't Find The Leak


Soap all, not just the joints.

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Old 04-19-2007, 03:12 PM   #3
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Re: Gas Line - Can't Find The Leak


try another guage
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Old 04-19-2007, 03:17 PM   #4
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Re: Gas Line - Can't Find The Leak


Yea .....thats the ticket ....crank her on and have a smoke.
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Old 04-19-2007, 03:34 PM   #5
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Re: Gas Line - Can't Find The Leak


When I was a kid in England we had a gas leak in the kitchen, the guy (chap!) came and found it by using his lighter! After the initial "whoomp" there was a six inch tall flame coming up between two tiles on the floor!
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Old 04-19-2007, 08:27 PM   #6
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Re: Gas Line - Can't Find The Leak


The best liqued detector is what the gas company uses. At times in the past, I have been able to beg some from them. Or ask the gas company to bring thier expensive sniffer to the job site.

What I have found in no particular order:
1. If you are using bushings between the gauge and the test port, toss the bushings.
2. Use a new gauge w/o bushings.
3. Put a valve on the test inlet. After pressurizing the line, close the valve.
4. Remove any gas valves and regulators. Plug where the valves and regulators where.
5. Do not test any fire suppression shut off valve over 10 PSI. To do so will ruin the automatic valve.
6. use only merchant couplings. The coupling that came w/the joint of pipe has straight threads,not tapered threads.
7. The connection that is the most dificult to repair is the leak.
8. put a bit of tape on the gauge to mark the pressure.
9. Dish soap is corrosive, don't use it.

I have had gas hold pressure at 20 PSI, but leak at 60 PSI. Don't test at more than the required pressure. Make the inspector show you in hte code book where you need to use more than 20 or 30 PSI.

Gas leaks can be a real problem to find. I'll take a leaky sprinkler pipe any day, they leak shut.

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Old 04-19-2007, 10:21 PM   #7
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Re: Gas Line - Can't Find The Leak


Make sure ALL appliances are disconnected before doing any pressure test above 5 PSI on the system; the controls cannot handle any high pressure. Also, most times a leak which is unable to be found is usually an internal leak of the gauge. Pull it---plug it---test it.
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Old 04-20-2007, 12:27 PM   #8
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Re: Gas Line - Can't Find The Leak


I will try your fixes but just incase i bought a bunch of lighters... It's a new run there are no appliances attached yet they are all capped. i will check the guage again but it is a new guage. We only pressure it up high to try and find the leak. I would hate to have to pulled this "crap" all apart. it's alot of pipe and fittings. All the pipe savers were not used in joining the lengths and bushings were replaced to eliminate that possible problem.

The saga continues. will keep you up to date
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Old 04-22-2007, 09:02 PM   #9
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Re: Gas Line - Can't Find The Leak


Several fittings had leaks in the fittings not at the threads. Lighters are magic in finding gas leaks.
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Old 04-22-2007, 09:02 PM   #10
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Re: Gas Line - Can't Find The Leak


only kidding about the lighters
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Old 05-06-2007, 08:45 PM   #11
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Re: Gas Line - Can't Find The Leak


I'm a day late and a dollar short here...but, when the test guage drops very quickly it's usually a sign of a sand hole (usually a flaw in the fitting or pipe) a fast leak is unlikely even if fittings aren't tight enough.
If you can't find the leak on a slow leak - bump the pressure up substantially until you can hear it..I'll take a "hiss" over a sudden explosion from a lighter any day.

Using a lighter is outright insane...imagine if there's even a small amount of oxygen rich air mixed inside the gas line....think of a pipe bomb.
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Old 07-09-2007, 09:47 PM   #12
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Re: Gas Line - Can't Find The Leak


Quote:
Originally Posted by Grumpyplumber View Post
I'm a day late and a dollar short here...but, when the test guage drops very quickly it's usually a sign of a sand hole (usually a flaw in the fitting or pipe) a fast leak is unlikely even if fittings aren't tight enough.
If you can't find the leak on a slow leak - bump the pressure up substantially until you can hear it..I'll take a "hiss" over a sudden explosion from a lighter any day.

Using a lighter is outright insane...imagine if there's even a small amount of oxygen rich air mixed inside the gas line....think of a pipe bomb.
Well put. I've heard that you can jab the lead of a pencil in the hole & break it off and it will hold. I've never done this due to ethics, but I'll bet someone will after reading this. Let me know how it works out. Also heard you can take a chisel and hammer lead between the fitting and pipe threads and it will fix the leaking threads. I know some lazy plumbers
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Old 07-10-2007, 12:31 AM   #13
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Re: Gas Line - Can't Find The Leak


If there is a pressure test on the new pipe there shouldn't be any gas in it yet. The lighter isn't going to do much unless the leak is enough to blow the flame.
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Old 07-10-2007, 09:02 PM   #14
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Re: Gas Line - Can't Find The Leak


Quote:
Originally Posted by thom View Post
If there is a pressure test on the new pipe there shouldn't be any gas in it yet. The lighter isn't going to do much unless the leak is enough to blow the flame.
Someone hinted at using a lighter on a live line...read the whole thread.
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Old 07-10-2007, 09:18 PM   #15
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Re: Gas Line - Can't Find The Leak


Quote:
Originally Posted by Grumpyplumber View Post
Someone hinted at using a lighter on a live line...read the whole thread.
I have used a match to find a small leak more than once and have never had more than a tiny flame at the leak. I am also talking about a leak that would loose like 5# from a 15# air test over night.
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Old 07-26-2007, 06:27 AM   #16
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Re: Gas Line - Can't Find The Leak


I've heard some of the gas company/contractor have a "Sniffer" to detect leaks, can't tell you much more, Good Luck
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Old 07-26-2007, 06:17 PM   #17
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Re: Gas Line - Can't Find The Leak


http://www.professionalequipment.com...gas-detectors/


$120.00.... small price, well worth it. I have one on the service truck. Tech tells me it works great.


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Old 07-30-2007, 02:59 AM   #18
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Re: Gas Line - Can't Find The Leak


Quote:
Originally Posted by crb555 View Post
http://www.professionalequipment.com...gas-detectors/


$120.00.... small price, well worth it. I have one on the service truck. Tech tells me it works great.


CRB

I would by one of those in a heartbeat if i messed around with gas pipes. Well i'm assuming they work.
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Old 07-30-2007, 04:55 PM   #19
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Re: Gas Line - Can't Find The Leak


When I was an apprentice in Richmond, Va. We used a lighter all the time to find leaking gas mains. Didn't need it on Hi-pressure one though. Lo-pressure lines we always checked with a lighter. Freaked me out first time I saw it.

Seems that natural gas will not travel backwards through a copper screen! Pull the sreeen away from the leak, and the burning gas followed the screen.
That's how gas companies burn the excess vapors above their plants, to the best of my knowledge. Screens in the stacks.
Did it hundreds of times, and NEVER got used to it.
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Old 07-30-2007, 05:00 PM   #20
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Re: Gas Line - Can't Find The Leak


I forgot to mention, we kept a 2" pipe with screen in it. We didn't just put screen against the leak and light it.

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