Best way to seal gas line threads, Pipe dope, teflon tape, or both? (2026 Update)

It's my understanding that the Teflon tape is not meant to be a sealant. It's purpose is to reduce the friction in joining threaded pipes so that they screw together more completely. The depth of the pipe in the fitting determines the seal, not the tape.

This notion seems semi-confirmed when you take apart a pipe and a fitting that's had Teflon tape used on the previous joint. The tape is usually shredded.

OMG! Let me get this right. You smelled a gas leak, but because a finished basement ceiling was involved, you just waited until you finally renovated the basement?

Suppose it involved the kitchen ceiling, would you have waited 15 years until you renovated the kitchen?

Well it was more like a couple of days, but I see your point.

Having said that, while I am disassembling everything, is there any harm installing another shut-off valve? This way in the future if I have to do any work, I do not have to go to my gas main and shut down the whole house. With this new valve, I can still keep the furnace and hW heater going. Downstream of this new valve would be my stove and dryer.

Don't know about where you are, but around here the rule is still pipe dope only for iron gas pipe.

Alabama gas techs use a Teflon containing pipe dope made by Oatey.

PST.... Loctite 567. When only the best will do.

nb

Either one, if used in accordance with the manufacturer's instructions for an approved purpose, is equally effective.

Either one. Yellow teflon for gas or dope, theyre both a standard for sealing gas pipe. That goes for unions too. Just make sure you crank down hard on on your connection either way you go, black pipe can take it.

Depends on what you mean by union. I agree dope or tape is appropriate for the threads that connect to the pipe, but it does no good on the threads that close the union, at least as far as preventing leaks. Those threads are not involved in sealing. It might help in making them easier to take apart someday, but I've never bothered.

Just make sure you crank down hard on on

The only difference in yellow teflon and white is the thickness (and the color, doh! :) ). It just takes more wraps with white to get the same amount is all...there isn't anything about the tape itself that is any different for gas specifically.

Yes, the threads that pull the union closed should not have anything on them, maybe oil to lubercate. As they do not seal anything , they just need to pull the two pieces of the union together.

I do like the dope over the tape if the joint is not likely to be taken apart.

This is the first time I have replied to a blog or post regarding the repair of a gas line. You can use pipe dope, teflon tape or both. My suggestion is to use both as a guarantee. If you are a home owner and doing the repairs yourself, you should know that both are designed to adjoin and seal any gas leak if gas lines are tightened properly. Yellow tape, designed for gas pipes has a higher density than the white tape used for water. That is the only difference, but since most respectable contractors use yellow tape for gas, I would suggest you do the same and follow it up with some pipe dope, also made of teflon to ensure you have a nice seal. After that, check if there is a leak by spraying soap and water onto your newly installed joints. If there is a leak, you will see bubbles. Hope I helped.

The experts ALL say - USE ONE ONLY. The thicker (generally pink) tape is made for gas fittings. Teflon paste also works well. The "stick" or "crayon" type pipe dope is a lot less effective and "I" won't use it again.

Use the tape - alone. Or use the dope - alone - IF the dope is still fresh and well mixed.

On 9/4/2019 8:41 PM, Clare Snyder wrote: ...

I use dope, usually. Faster. Any inspector that sees both is going to know that it was an amateur job. Some people think that more is always better, even though many times it's not.

The purpose of the tape is not to seal the joint, but rather to force matching tapered threads into each other to create a gas-tight seal.

Tape will not seal parallel threads.

Yellow is the standard tape color for use in natural gas piping systems.

Same here - it is generally referred to by it's Dupont trade name - TEFLON