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I'm replacing a faulty regulator on my gas grill. When removing the old regulator, I noticed there appears to be some sort of compound on the threads.

Here is a picture of the threads with the old regulator still partially attached: Regulator still attached

And here is a picture of the threads without the old regulator attached: Regulator not attached

Questions:

  • What is that substance, and where can I get it?
  • Is it required in order to protect against LP leaks?
  • Are there any tricks or gotchas to know about when applying it?
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The tape you purchased is the correct tape for gas fittings. However, the fitting in your picture is a flared fitting. PTFE (Teflon) tape/pipe dope is only necessary on pipe thread fittings.

This is because pipe threads are tapered - as you tighten the fitting, the threads bind together and deform slightly to create a seal. The pipe tape/dope helps lubricate the threads and make a better seal.

With a flared fitting like your photo shows, the flare at the bottom seats in a mating flare inside the female fitting. The threads are only there to draw the two together.

Using tape on the flare fitting may not cause any problems, but I would not take the chance, especially with gas. If any tape gets under the flare or prevents the nut from tightening down fully, you're going to have a leak.

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  • This comment needs to be the accepted answer. If people use too much thread tape (and you know somebody will), it can keep the nut from screwing all the way down, which will keep the flared end from making tight contact with the nipple. And then you're just taking your chances that the blob of thread tape in those non-tapered threads is going to hold the gas in. Scary. – msouth Jun 17 '14 at 13:25
  • Based on feedback, I have marked this as the answer. – Jon Sagara May 9 '15 at 0:46
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Dangerous advice warning: As pointed out in the comments and other answers, this is the improper solution for a flared gas fitting.

Just got back from the hardware store with this:

Thread Seal Tape for Gas

It's apparently similar to Teflon tape that you would use on a water fitting, but made specifically for gas.

There is also a compound available, but I chose to use the tape because I was told that the compound can be a bit messy.

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  • According to Wikipedia, you can get teflon tape in different colors to match the use. en.wikipedia.org/wiki/Teflon_tape#Types – Jay Bazuzi Jul 31 '11 at 19:17
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    The tape above is fine, use 3 or 4 complete wraps. If you use a liquid dope, be absolutely sure it is LPG rated and apply it with a acid brush. – shirlock homes Jul 31 '11 at 20:18
  • This answer incorrectly implies that it is safe to use thread tape on a flared fitting (the bottom fitting in the posting's picture). You do not want thread tape there as it might impede the complete tightening of the flared pipe against the opening. The seal in a flared fitting is made by how tightly the flared pipe is held against the nipple it is connecting to. "Teflon" tape or pipe dope is used on tapered pipe fittings, where the seal is actually created by the threads themselves. Please correct this, as you are risking a gas leak for yourself and anyone that reads and follows this. – msouth Jun 17 '14 at 13:22
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Use of thread seal tape does not work on the fittings that screw directly into an aluminum propane regulator. I don't know if the changes in seasonal temperature cause the aluminum to contract and expand (or something else) but six months later the fittings will be loose and leaking. I suggest using a hardening compound.

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