Leaks on gas pipe, any advice?

[phishfood]

Strange as it may sound, I have done almost no gas pipe before. We are plumbing an apartment complex with black iron for the gas pipe.

We have had a lot of trouble in the first building with leaks at the thread joints.

So now, I am piece working the gas pipe, and have had 3 leaks so far in the 3rd building ( 1st building I have done).

Putting aside the fact that I make less money when I have to go back to fix leaks, and the even bigger fact that it wounds my pride to have leaks, it is scary that we are having so much trouble getting the joints to seal.

The pipe is cut and threaded on a Ridgid 300 T5 machine, with new dies. The threads look good, and seem to thread into the fittings well. We are using Whitlam Blue Magic pipe dope. I am certain that I tightened everything up sufficiently, none of the leaks I fixed today were loose when I unthreaded them.

What could be the problem, and how can I resolve it?

[majakdragon]

If the pipe threads are good, start looking at the threads in the fittings. My "rule of thumb" for threaded joints is that they should tighten up at 3 rounds by hand, then tighten the rest of the way with a wrench. If the pipe is going in 5 or 6 threads by hand, the fitting threads could be worn or oversized. Pipe joint compound is merely a lubricant and not made to actually seal the joint. I use Rector-seal 5 on gas lines. Just a thought.

[Reedwalker]

I am a fan of Blue Magic. Thats what I use on everything.

The 3 rotation rule is a standard and I use it as well. Also when cutting the threads I only allow the pipe to come through the farthest tooth on the die one thread. Meaning, the pipe really doesn't come to the "outside" of the die. It only comes just past the last tooth of the die.

When I am doing large systems I employ the dope, tape, and dope rule. On 1/2" pipe only dope is necessary. On 3/4" pipe I use 4 wraps of good quality teflon tape and dope on top of it. On 1" and above I use dope, 4 wraps of tef tape, and re-apply dope.

It's a couple extra steps, but once you get in the habit it doesn't really add that much time. And chasing a leak on a large system can literally take all day.

[majakdragon]

I am not a fan of "double doping" pipe but have done it in the past. I did a job at a Tefon manufacturing plant in Michigan and they required teflon on all joints. We had a 3" line that we could not get to stop leaking so we snuck some Key Tite compound onto the lower threads. It held the first try. I also don't apply any compound or teflon on the first two threads at the end of the pipe. Pipe threads are tapered and there are times the first couple threads do not lock into the fitting. This allows any excess to get into the piping.

[phishfood]

Thanks for the advice.

I neglected to mention that I adjusted the dies to cut so that a fitting threads on the 3 turns by hand. But thanks for mentioning that, would be good to know if I didn't already.

I do know that some of the guys at our company used to use tape and dope on gas pipe, and I always do on waterpipe. But the office told us all some time back to use only dope on gas lines. Supposedly natural gas can deteriorate the teflon tape or something?

I have glanced at the fitting threads a few times, but I will make a point of checking a good number of them tomorrow.

[ProFlowPlumbing]

I never use teflon on gas pipe.I used to get leaks with teflon.Now i use Slic Tite or Rector Seal on both the male and female threads.NO LEAKS EVER THAT WAY
I also use the 3 turns by hand rule.

[Mr_David]

Originally Posted by ProFlowPlumbing

I never use teflon on gas pipe.I used to get leaks with teflon.Now i use Slic Tite or Rector Seal on both the male and female threads.NO LEAKS EVER THAT WAY
I also use the 3 turns by hand rule.

You don't want to put dope inside a female fitting. But I am guilty of the same on occasion. I like using Key-tite. Dark green and a little messy.
2 warps of teflon is best. To much and it just gets pushed out as you screw it toghether. If I use tape I don't dope the pipe first. You'll want to wrap the tape tight. If it's loose you'll just push it out of the joint

I agree on cutting threads one thread past the last tooth of the die.

Also when you're tightening the joints you don't have to make them super tight.
You want them tight but you don't have to put every thing you have into it.
I've split fittings before.

[CHRISM]

I am based in the U.K. where we have to be separately registered for Gas Installations - AND be reassessed every 5 Years [Exams - Practical AND Theory] - Extremely Technical Exams.
And the products that are `Approved` for use on Gas Installations are `highly regulated`.
`Ordinary` Plumbing and Heating Teflon tape [PTFE] is NOT ALLOWED in the U.K. for use on GAS - this has been the case for YEARS and is the result of testing by a number of very expert organisations in the field of Gas Utilisation - which revealed that the `ordinary` Teflon tape was not suitable as it was `too thin` and `did not seal correctly` - also it was found that it did `degrade` over time - making a risk of leakage.
At the time of those `findings` - I questioned the `too thin` result with regard to the amount of `turns` of tape - to be informed that the `Approved` Gas version of the teflon tape [that we have used since] is a Completely Different `make-up` - much thicker tape AND a different Teflon make-up, needing much fewer turns around the pipe to seal the joint.

As to the Tape AND Jointing Compound - that is Not something that we do in the U.K. on `small bore` Gas pipework [up to 1"] - although it is probably carried out on larger pipe sizes.

Our jointing compounds are varied - including liquid Teflon [PTFE] - and on correctly cut threads and decent quality fittings - we use only a Jointing Compound OR - Gas Teflon tape for small bore Gas pipework - NOT both.

[Briansnorthstar]

Although I now live in N.C. I am from Maine and in Maine teflon tape is not allowed in gas piping.
To be honest I am not sure of the code here but will look it up

[havasu]

Are you referring to the white teflon tape, or the yellow "gas approved" teflon tape? I hate using teflon tape for anything anymore. I'm completely sold on Rectorseal # 5. It coats, lubricates and seals when coupled to another pipe.