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:
And here is a picture of the threads without the old regulator attached:
Questions:
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.
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:
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.
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.
