Help Locating Small Pressure Leak Black Pipe

[MrMark]

I am doing a 15 psi pressure test on the black natural gas pipe I put together. I have done this quite a bit and I absolutely hate working with this pipe because of the trouble it is to get leak free fittings even when completely properly made up. I use Rectorseal T2 plus teflon and tighten very well, never back up a fitting and make sure the fitting is not bottoming, etc. Still have problems at 15 psi test, although it does not leak at the .25 psi line pressure. This is why plumbers use tape and dope almost universally but I am too stubborn to do what I consider an improper procedure.

Anyway, help with finding at least one tiny microscopic leak! It leaks down maybe a psi over an hour! I have made up soapy water spray and I hate using it. A mess and it might not cling right. When I have done this before I note these micro leaks take a long time to show a bubble.

What is the best method to find this micro leaker?

 

[MrMark]

Update: I started at 15 psi at 7:00 pm last night and I saw it move down to 14 by 10 Pm. It has been overnight and now 2:00 Pm the next day and it is at 12 psi and stopped!

How the hell am I going to find a leak that only leaks at a microscopic rate from 15 to 12 psi?

How weird is it to have something that leaks at 15 but holds at 12?

This black pipe and foreign fittings has got to be the most frustrating stuff of all building materials to work with. I can't imagine trying to plumb high pressure air in this mess.

 

[Steevo]

I had one that lost 1psi a week. That is a slooooowww leak. I soaped all joints several times, and found no bubbles. Then I decided to buy a new pressure guage. Guess what was leaking?
THE GAUGE!

 

[bmwpower]

Spray Windex on the joints. Bubbles up nice and dries better than water and soap.

 

[MrMark]

HA!

There are no leaks! I pumped it back up from 12 to 15 and it hasn't moved in two hours.

Here's what happened: last night just about when I pumped up the system a weather front moved in and it started to sprinkle. Then it rained, heavy at times, in the morning.

My theory is that the falling barometric pressure affected the gauge and caused the gauge to fall 3 psi!

Anyway, that has to be it because it is now holding steady and I did nothing to the system other than spray around a little looking for leaks, of which I found none.

BMW, thanks for that tip!

STEEVO: it was the gauge and the weather!

 

[nutjob]

HD and plumbing supply sell the correct stuff for leak checking.
It is a thick fluid and has an applicator that looks the same as the PVC cement. (big cotton ball on the end of a rod attached to the cover)

If you are looking for a tiny leak, this stuff is the right tool for the job.

Kevin

 

[Andamo]

Yep, that's what is was. There isn't much volume of gas in the pipes and the temperature getting colder reduces the volume. When we pressure tested high pressure reactors and associated vessels, we had to take into account the room temperature and barometric pressure. One of our enginners actually came up with a correction program and all we did was plug in the pressures, temps and barometer before and after pressure testing and it would give us the true leakage rate.

 

[ishiboo]

Glad it worked for you. I've heard that the newer black pipe fittings are not as high quality as the old ones, and rely a lot more on dope to get them to not leak.

I've never worked with black pipe and never plan to... CSST seems a lot more DIY-friendly.

 

[rodnok1]

If it was still leaking I would actually check the pipe seams/caps/elbows not just the joints. I've had a couple elbows and caps be so porous they leaked.

 

[MrMark]

If it was still leaking I would actually check the pipe seams/caps/elbows not just the joints. I've had a couple elbows and caps be so porous they leaked.

No, it's all good now. I appreciate the comments, it held steady for 6 hours or so before I pulled the test and put the shutoff valves back in and put it back together. A couple of things I learned is because of the small volume of gas (air) under test, tempurature and barometric pressure affect the reading significantly, enough to make it look like a leak.

I was really worried that I might have just what you posted, a pin hole in a rusting underground pipe, or fitting. Black pipe is a challenge to do correctly and get leak free fittings without resorting to the tape and dope combo trick, which I do not think is a good idea long term.

I wish there was a better way to do natural gas, but the CSST is problematic as well and you have to be a certified installer to make up the fittings I have heard about. CSST also has lightning strike issues and it is not resistant to puncture from a stray nail or screw. Overall, black steel is the best way to go but it is a ******* to work with.

 

[59 wagon man]

just a quick tip do not rely upon a gas **** for a pressure test .they do not hold a lot of pressure and many a test i had to redo and learned to always cap off the plug type gas valves

 

[bmwpower]

HD and plumbing supply sell the correct stuff for leak checking.
It is a thick fluid and has an applicator that looks the same as the PVC cement. (big cotton ball on the end of a rod attached to the cover)

If you are looking for a tiny leak, this stuff is the right tool for the job.

Kevin

Why is this is the right stuff?

 

[MrMark]

just a quick tip do not rely upon a gas **** for a pressure test .they do not hold a lot of pressure and many a test i had to redo and learned to always cap off the plug type gas valves

Yes, the code test requirements are to remove the shut off valves at each appliance and cap the hard pipe stub outs. It makes for a lot more work to do a pressure test.

I also found during this test that the gas meter shut off valve did not completely shut off the system. I found this as you have to remove the spud on the customer side of the gas meter to screw in your pressure gauge with schraeder valve to the house's piping. I put the spud back on and capped the ****** and had the gas co's valve shut off. When I went to put it back together I undid the nut on the spud and a little gas poped. The gas co's valve is bad.

 

[MrMark]

Why is this is the right stuff?

I've purchased this before and used it some. I can't remember why, but I know I was dissatisfied with the way it worked and switched to the spray bottle with a heavy dawn to water concentration. I think it made a mess.

 

[jhelrey]

What are you running through the pipe? Air, LP, what?

 

[MrMark]

Natural gas.

 

[MrMark]

Gas co came out and said it is normal for a little gas to "bypass" the supply side shut off valve as it is exposed to 40-60 psi from the main line in the street.

 

[Hlidskjalf]

There is nothing wrong with black iron gas pipe, only with the installer. I have been installing gas lines since I was 15 years old and I have never had a leak. I would recommend using pipe dope only and properly apply it.

 

[59 wagon man]

Yes, the code test requirements are to remove the shut off valves at each appliance and cap the hard pipe stub outs. It makes for a lot more work to do a pressure test.

I also found during this test that the gas meter shut off valve did not completely shut off the system. I found this as you have to remove the spud on the customer side of the gas meter to screw in your pressure gauge with schraeder valve to the house's piping. I put the spud back on and capped the ****** and had the gas co's valve shut off. When I went to put it back together I undid the nut on the spud and a little gas poped. The gas co's valve is bad.

we would usually disconnect the appliance at the flex connection and cap it there just needing to remove the adapter and replace with a cap. the valves we would leave in the open position instead of removing them we would disconnect at the flex or union and either cap or plug the easiest fitting . in the long run it isn't much more work . one time when i was a helper we had an apartment building in the bronx with 250 apts that we needed to install a 3" gas valve for a 1,000,000 btu water heater .instead of shutting all the pilot lights we made a manifold and connected some kind of gas(dont remember exactly what) shut off the main while the bottled gas fed the building and installed our new valve. we only had to relight a half dozen or so pilot lights

 

[danski0224]

There is nothing wrong with black iron gas pipe, only with the installer. I have been installing gas lines since I was 15 years old and I have never had a leak. I would recommend using pipe dope only and properly apply it.

I made a test manifold for a hydronic system so it could be pressurized while the concrete was poured.

Several joints leaked with only pipe dope. The leak showed up underwater.

I had to do dope + 3 wraps of Teflon tape. One ****** had a burr on the threads.

The Chinese fittings and pipe sold these days *****, and it is almost impossible to get US made product. US made fittings are nicer and the pipe threads much better (not full of rust, either).

Instructions for a tankless water heater isolation valve setup calls for a minimum of 5 wraps of Teflon tape. That is what I do now.

And yes, the Teflon sold on the little rolls at the hardware store is much thinner than the "pro" stuff.

 

[Hlidskjalf]

I made a test manifold for a hydronic system so it could be pressurized while the concrete was poured.

Several joints leaked with only pipe dope. The leak showed up underwater.

I had to do dope + 3 wraps of Teflon tape. One ****** had a burr on the threads.

The Chinese fittings and pipe sold these days *****, and it is almost impossible to get US made product. US made fittings are nicer and the pipe threads much better (not full of rust, either).

Instructions for a tankless water heater isolation valve setup calls for a minimum of 5 wraps of Teflon tape. That is what I do now.

And yes, the Teflon sold on the little rolls at the hardware store is much thinner than the "pro" stuff.

I've laid thousands of feet of pipe with pipe dope only. I don't really know what else to say.

I never had problems with leaks. T-Tape works okay, I keep in on my tool belt so I don't have to run to my truck with some simple service work. Code around here prefers dope over t-tape. I use dope as much as possible.

 

[MrMark]

There is nothing wrong with black iron gas pipe, only with the installer. I have been installing gas lines since I was 15 years old and I have never had a leak. I would recommend using pipe dope only and properly apply it.

I love it!

Plumbers who have never had a leak and have been doing it all their life. Sort of like the shower door installer who has never had a leak or the mechanic who has never had a come back. Some are just perfect it seems.

Code has no preference for dope over tape. That's BS. Show us the code.

Honestly, I doubt you have any clue whether you have had leaks or not. Did you pressure test every installation of black pipe that you have done? Didn't think so.

 

[MrMark]

we would usually disconnect the appliance at the flex connection and cap it there just needing to remove the adapter and replace with a cap. the valves we would leave in the open position instead of removing them we would disconnect at the flex or union and either cap or plug the easiest fitting . in the long run it isn't much more work . one time when i was a helper we had an apartment building in the bronx with 250 apts that we needed to install a 3" gas valve for a 1,000,000 btu water heater .instead of shutting all the pilot lights we made a manifold and connected some kind of gas(dont remember exactly what) shut off the main while the bottled gas fed the building and installed our new valve. we only had to relight a half dozen or so pilot lights

The requirements as I know them are to remove the valve and cap the hard pipe. The valves and flex connectors are not rated for the test pressures. The valves are 5 PSIG max.

 

[Hlidskjalf]

I love it!

Plumbers who have never had a leak and have been doing it all their life. Sort of like the shower door installer who has never had a leak or the mechanic who has never had a come back. Some are just perfect it seems.

Code has no preference for dope over tape. That's BS. Show us the code.

Honestly, I doubt you have any clue whether you have had leaks or not. Did you pressure test every installation of black pipe that you have done? Didn't think so.

Lawl...

Code here is very strict, and I definitely wont go though the effort of scanning my code book to prove you wrong. Believe whatever you want, I don't have the problem with leaks, all my jobs are leak free and pass code.

You made the thread asking for help. Good luck getting anywhere with that attitude.

It's gas pipe, not rocket science. I have definitely had leaks, but not due to improperly doped threads.

 

[MrMark]

xxxxxxxxxxxxxxxxxxxxx.

NO WORRIES!

 

[Hlidskjalf]

Sorry MrMark, from what I gathered there was initially an issue with doping/t-taping the threads and leaks with the black iron pipe. Since most leaks in a freshly installed gas piping are usually caused from poor installation methods I figured I would point that out as a possibility.

I never intended to say that you are not capable of doping threads. I did notice that you figured out the problem to your leaking pressure test, good on you.

No insult was intended anyway. Good luck with your future gas piping.

 

[danski0224]

I never had problems with black piping as long as US made pipe and fittings were used.

Not true with the Chinese junk.

 

[walrus]

I never had problems with black piping as long as US made pipe and fittings were used.

Not true with the Chinese junk.

Thats the key, I buy Ward fittings at a plumbing supply house. The pipe is usually made in Canada. Why bother getting frustrated using junk from Home Depot or Lowes. I also hate teflon tape. Rectorseal no 5 is the only thing I use and for the amount of piping I've done, I've had very few issues.

 

[nate379]

Wow, I would have called it good if the pressure was fine in 2-3 hrs! The last few gas lines I have done I used yellow tape with Rector Seal and was fine.

I never pressure tested though, just soapy water, which is all the gas company does as well.

I had one that lost 1psi a week. That is a slooooowww leak. I soaped all joints several times, and found no bubbles. Then I decided to buy a new pressure guage. Guess what was leaking?
THE GAUGE!

 

[D.J.]

Nate379; I don't want your gas company on my property doing ANY work for me! I have a hard time beliving they would not do a leak check with pressure guages on an existing system or a pressure test on a brand new system as required by code.
________
EXTREME VAPORIZER Q

 

[csp]

Why is this is the right stuff?

Because with a very small leak a soapy water mix won't stay on the joint long enough or will dry out before a bubble forms.

There's a kind in a tube with the applicator and one that is in a spray form. It's very viscous and stays where you put it instead of running off or drying out.

 

[MrMark]

Plumbing supply houses have the same fittings as Home Depot and Lowes, around here. All they do is mainly charge more for them. Just like the lumber yard has just as bad wood and charges more.

 

[MrMark]

Because with a very small leak a soapy water mix won't stay on the joint long enough or will dry out before a bubble forms.

There's a kind in a tube with the applicator and one that is in a spray form. It's very viscous and stays where you put it instead of running off or drying out.

That's the problem I've had in the past. It needs to cling and hang in the joint without making a total mess. I'll take a look and see if there's any better stuff next time I'm in a plumbing supply.

 

[nate379]

Pointless to fight because you will be right no matter what I say but that is what is done.

Nate379; I don't want your gas company on my property doing ANY work for me! I have a hard time beliving they would not do a leak check with pressure guages on an existing system or a pressure test on a brand new system as required by code.

 

[truckman5000]

Pointless to fight because you will be right no matter what I say but that is what is done.

Yah i agree, that is whats done.
Gas c/o dose a bubble test on repairs. So do I(and ur lucky if your plumber is even doing that) No sence in pressure testing 3 joints.
The code here on a new system is the test has to hold 5psi, with a 10" inch guage for 15 mins. If there was a small leak on that type of guage yould see it in 15 min. Inspectors dont care if the guage gose down because of atmosphiric pressure. As long as theres "air pressure" on the test it passes.