Do you use any sealant on the gas line fittings?

[green69rt]

Starting to put the fuel system together and wondered.  I don't think I have used any type of sealant on the fittings.  I think they are all NPT with the tapered threads.  My gut feeling is none but not sure.  If a sealant is used, guess I would go to Oreilly's and look for gas and oil resistant material.  I'm pretty sure I can't use teflon tape that I use on water pipes.

[birdsandbees]

Loctite PST-592 on ANY pipe thread, or it's gonna leak.

[BSB67]

Interesting. I almost never use sealant and never have a leak.  I do always use some lubricant.

[green69rt]

I should have read the instructions on the Carb line kit before asking.  According to those instructions, if it doesn't have an "O" ring or flared fitting then sealant is required.  The exception is a fitting called NPTF that are specific for fuel.  Never seen one.  Oh, and the instructions say teflon tape is OK.

[Nacho-RT74]

I never have needed to use it but If I do... maybe teflon tape ?

[John_Kunkel]

Just got off the phone with a friend whose engine break-in was cut short by a flooding carb. The culprit? A pieced of Teflon tape in the needle valve.

When applying Teflon tape or paste to a NPT fitting, never apply it to the first thread...start one or two threads up.

[Nacho-RT74]

sure!!! thats what I do! althought as mentioned never have need it on a gas line

[green69rt]

Looked at the transmission cooler lines.  Those look like NPT.  Little short threads.  I will be careful with the tape. Need to go to O'reilly's for some fittings so I'll look for the Loctite PST-592. 

[Bronzedodge]

X2 on what John Kunkel said.  Teflon sucks for anything where small bits of the stuff will cause a problem.  In the fuel oil world, most device manufacturers say no teflon on oil.  It gets semi-dissolved and then clogs the pump, valves, etc.  In some places it is against code.  Many gas device mfgs say the same thing.  Never use it on fuel systems.  If it gets to the valves, you're done.  The other problem is the second time you put it together and teflon is caught in the female thread side - the bits get pushed in.
Pipe thread - American pipe is tapered.  Use a good pipe dope like Gasoila, Rectorseal, Blue Monster, etc.  Keep it one thread back from the end like John said.

[green69rt]

X2 on what John Kunkel said.  Teflon sucks for anything where small bits of the stuff will cause a problem.  In the fuel oil world, most device manufacturers say no teflon on oil.  It gets semi-dissolved and then clogs the pump, valves, etc.  In some places it is against code.  Many gas device mfgs say the same thing.  Never use it on fuel systems.  If it gets to the valves, you're done.  The other problem is the second time you put it together and teflon is caught in the female thread side - the bits get pushed in.
Pipe thread - American pipe is tapered.  Use a good pipe dope like Gasoila, Rectorseal, Blue Monster, etc.  Keep it one thread back from the end like John said.

I decided to forget about the teflon, found a tube of the PST-592.

[Bronzedodge]

I decided to forget about the teflon, found a tube of the PST-592.

Oh, the sticky stuff, off-white?  That is an excellent pipe dope.  We used it on the PITA stainless incinerator piping.  It works well.

[greycharger]

If cut correctly, threads do not need sealant. Pipe dope and teflon tape are lubricants that help make up the threads properly. NPT threads have a certain number of threads and the first few are tapered 2 degrees, so there is a sweet spot of thread depth and thread shape as fittings and pipe come together to seal by interference. If threads are cut too deep, the male goes too far in and leaks past the straight threads at the rear, too shallow and not enough threads are made up past the tapered threads, and can leak.
I use whatever oil or grease is closest to me at the moment. Then I watch how many threads make up before it gets snug, then how many after. Not enough or too many, replace.

[Bronzedodge]

In theory, maybe for certain applications.     In real life, all NPT needs sealant.     Put together threaded connections on high pressure steam and the tell me about no sealant.