[unofornaio]

Hi all,

I am in the process of adding a new coated 1/2" natural gas line underground to a patio area.

I wanted to pressure test it before I bury it and I cannot seem to find the leak. I have a gas pressure valve from Home Crapo that goes up to 15psi. I filled the pipes up with this on and cannot get it to hold @ 15 psi for more than a few hours, in about 3hours it drops about 1/2 psi or 3/4.

I have coated all the threads with a good quality gas pipe dope, (Rectorseal 5) and everything is nice and tight. After cleaning the excess dope off I coated the pipe with varying degrees of a soapy solution and I cannot see any bubbles. I have installed gas line before adding on to an existing line and have never had a problem like this. Of course I have not pressure tested before just checked with a soap solution while the gas was on.

I thought it might be the gauge so I took the 8" stub a cap and a 3/4-1/2 bushing (to adapt to the 3/4" gauge and just tested this but I still get a loss of psi. Am I under the wrong impression that this should be completely air tight? I found an old thread (Aug 2005) on this forum that said 10 psi for 15 minutes. Can someone tell me what the national code is for this and perhaps explain what I should expect to happen. I would really appreciate it. I'm going to be adding more pipe to this but wanted to test this area so I can back fill it right now. This is not going to be inspected but I want to do it right.
Sorry for the long post but I offer advice as a masonry/concrete expert on a forum and seems like I always have to ask for more info before giving an answer I can live with.
I hope this is enough info. I have another question about using a ratcheting threader but I will reserve that for later. All this pipe has factory threads.
Thank for any help

[brich0]

Hi, I am facing a similar situation. I do believe that my gauge is holding pressure, but I seem lose about 1/2 psi every couple hours and cannot spot a leak. How did you resolve the problem?

[letmetellu]

If you do a test lie the guy above with a short nipple and over 20 psi and it shows you have a leak then hold the entire part, gauge, nipple and cap, to see where the bubble is coming from. If you do not get any bubbles it may be that the temperature is changing and showing a small drop in psi. But if you put it back on your line a show a drop in psi, you then need to do a soap and water test of you piping, making sure that you soap all joints and also all over any fittings.

The service company that supplies your gas determines if you can have a small leak or not. In my area you can not have a leak at all.

Hope you find it.

[massplumber2008]

Hi Brich0

I'd suggest that you disconnect the piping from any appliances, gas valves and the gas meter and then test the gas line to say 25 or 30 PSI. Then take a soapy solution you make up and spray all the joints on the exposed joints.

If that fails to expose any leaks you will need to dig over to each fitting underground and soap each underground joint. You may even need to increase the pressure to 40-50 PSI.. ;)

Did you pull a permit for this work? If so, the inspector will want to see every joint.

Finally, if you call the gas company they will not help you unless a permit has been acquired. Just FYI!

Any questions... let us know...

Mark

[brich0]

Thanks for the fast reply, I did pull a permit for the work, and there are not appliances connected. I am replacing an underground gas line from my home to my grill (it was undersized and didn't seem to be done well). The existing lines include a tee in the black iron in the house, followed by a shutoff, a union, and a length of pipe with a couple turns to get out of the foundation. This is where I started. After removing the existing black iron fittings directly outisde the foundation, I added some black iron fittings to make a sediment trap and ended with a union. From the union, I go through an anodeless riser to a coupler to ~80 feet of PE to another coupler, anodeless riser, and a shutoff valve. I did not cut any threads myself.

My pressure gauge (I have capped the gauge, it seems to hold and work ok) is on the very end near the grill after the shutoff. I leave this shutoff open. The shutoff in the house is closed. My intent is to ensure all piping between the existing shutoff in the house (which I didn't touch) and the end of my new pipe (which after pressure tested will have a quick disconnect for th BBQ) is tight.

After bringing the pressure up to 15 psi, it seems to lose about 1/2 psi every few hours. I have soap tested all of the metal joints and found no leaks. The couplers for the PE are difficult to soap test, but I have tried and found no leak.

Any other ideas? Is it OK to up the PSI using PE? I am reluctant to try and remove the shut off in the house can cap it because it seems very difficult to remove, I am worried about causing more harm than good?

[massplumber2008]

Hi Brich...

This question has gotten a bit messy as I kind of answered your question and uniforniao's question at the same time. I'm on the same page with you now.

Tell me what is PE pipe? And did you say an 80 foot run? Any underground?

Let me know and I'll be able to finish answering your questions.

[brich0]

By PE I mean polyethylene(sp?) plastic yellow gas pipe for direct burial. The 80ft of pipe is currently in an open trench awaiting a successful pressure test and subsequent inspection and backfill. I looked up the pipe, risers, and couplers, and each is rated for 100+ PSI.

Thanks!

[massplumber2008]

Remove the gauge and disconnect the piping at the union and cap it off. Then pump the system up to 50 PSI or so... then try soaping again... should reveal the leak for you.

Let me know...

[brich0]

I went through and broke the union and capped off the pipe inside the basement. This *appeared* to hold (it dropped from 30 to 29.5 overnight, I thought it was temperature related). To me, this meant that the old shutoff was leaking a little bit. I pulled the cap, changed the union and shutoff in the house, and started over. It held 30 psi from 10am to 4pm, then slowliy starting losing and at 830am is at 26.5 psi. I don't think it'll come back up with the temperature, but I don't have the experience to know.

The gauge I'm using includes the air valve for pressuring the line so I can't remove the gauge, and it maxes at 30 psi. I think I'll have to go out and buy a 0-100 gauge and use that to put in say, 80 psi to find the leak?

[brich0]

Another question, is it likely that there is nominal leakage through the shutoff valve packing nut or across the valve?

[ma0641]

Some of the old gas valves were tapered with a spring and nut assembly to hold the valve tight. I've seen some of them leak around the valve. You can shut off the gas, take the valve apart, polish it with emery paper, LIGHTLY oil the surfaces, reassemble and tighten the nut. At least worth a try.

[ma0641]

Older gas valves were tapered and with age can leak when the spring weakens or the bottom nut backs off. If you have an old style valve, shut off the main gas supply at the meter, take the suspect valve apart, clean it with mineral spirits and polish with emery cloth, clean with mineral spirits and LIGHTLY oil the valve and seat. Reassemble and tighten the nut so that it is somewhat hard to turn the valve handle.

[massplumber2008]

If you have an old shutoff then I have no doubt that is where you are losing the pressure... what happens when you soap up the nuts and washers on the back of the old shutoff at 30 PSI.. leak would show pretty quick? If leaking here, tighten the nuts a 1/2 turn and see if that improves things.

Otherwise, I'm going to go with temperature being the culprit here. In my area we are required to use a very special test gauge that measures in 1/10th PSI increments so any leak shows up pretty quickly.

If you pump this up and it held at 30 PSI for 6 hours, I think you're all set. Temperature and pressure are directly related so if the temp. went down so could the pressure.

If you are still unsure.. remove the gauge entirely and simply pump the line up to 50-60 PSI and do a last soap test. If no leak shows you are all set! Remember, in most areas you only need to hold the test for 10-15 minutes... ;)

Mark

[brich0]

Hi all,

In the end, it looks like I had two problems. First was the old shutoff which I replaced, and second turned out to be my gauge (which I had already checked, apparently not well enough). The grill gets extra hot now, time for a bigger one! Thanks for all of your comments, it was very helpful!

[Milo Dolezal]

Glad you got it up and running !

[BHR907]

I wouldn't run high pressure through any closed valves, they aren't designed for more than a couple psi, sounds like that might have been your problem

[massplumber2008]

BHR907 is misinformed (or guessing) when he/she says that gas valves (even older gas valves) are not designed to handle higher pressures... they sure are, they just happen to be used on low pressure systems... ;)

And passing "high pressure thru any closed valves" simply doesn't make sense... right?

Anyway, testing at higher pressures is the only way to find a GAS LEAK sometimes... simply no getting around that!

Mark