Best way to seal gas line threads, Pipe dope, teflon tape, or both?

During my basement reno, I discovered a small gas leak at one of the pipe threads in my gas line. Actually I suspected for some time there was a leak in this particular spot, but could never pinpoint it because of the closed ceiling. Now that the ceiling is gone, I have found the problem. So rather than try to take the cheap way out and try to seal it from the outside with epoxy, I am going to take everything apart, reseal it, then put it back. Its 3/4 black pipe.I want to do this once and do it right. What is the best way to seal the threads? I have both pipe dope, and yellow teflon tape for gas.
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Mikepier wrote:

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.
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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?

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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.
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On Tue, 11 Jan 2011 05:01:07 -0800 (PST), Mikepier

pipe dope only for iron gas pipe.
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On 1/11/2011 7:01 AM, Mikepier wrote:

Alabama gas techs use a Teflon containing pipe dope made by Oatey.
http://preview.tinyurl.com/6b7qqrp
TDD
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PST.... Loctite 567. When only the best will do.
nb
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Either one, if used in accordance with the manufacturer's instructions for an approved purpose, is equally effective.
--
There is always an easy solution to every human problem -- neat,
plausible, and wrong." (H L Mencken)
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