Pesky leaking connection on my air compressor

[mears]

I have an older craftsman air compressor that I picked up on craigslist that I recently restored. Unfortunately, there is a small leak around the check valve threads. I've tried varying wraps of PTFE (3 to 8) and varying levels of tightness, yet it keeps failing the soapy water test. This last time, I went a little overboard on tightening in frustration, so I'm hoping I didn't make the problem worse.

Any suggestions or alternatives to PTFE?

[Kartman]

I've had luck with heavy duty pipe sealant when it pertained to pesky threads that won't seal. It is a really thick paste for sealing coarse threads on the end of black or galvanized pipes. You should be able to find it at your local home center.

[porschedude996TT]

There is a tread sealant that is used in the Air Conditioning biz. Find a wholesaler and get a tube. It hardens like epoxy, but you can break it loose when you need to. The stuff that I have is light blue.

[mears]

Thanks for the suggestions. With either, would I continue to use PTFE or just rely on the other sealant?

Also, this valve doesn't have male pipe threads, it is coarser.

[Kartman]

Thanks for the suggestions. With either, would I continue to use PTFE or just rely on the other sealant?

Also, this valve doesn't have male pipe threads, it is coarser.

I wouldn't advise using the PTFE thread tape with the paste sealant. I think using the paste alone should cure your leak issues as it is designed for coarse threads. Comes both in tube form as well as in a bottle with brush applicator.

[mears]

Well, I went to Lowes and they had a couple different products that looked applicable. The first was Pipe Joint Compound, which was the cheapest, but had the highest pressure rating (up to 3000PSI on gasses) that is non-hardening and non-separating.

They also had two different types of Pipe Thread Sealants (Normal and Soft Seat). I would think that would be what I would want to get, but it only went up to 125PSI.

Is there any reason not to use Pipe Joint Compound?

I couldn't find the HVAC stuff locally, but Grainger carries it:
http://www.grainger.com/Grainger/items/2TRL1?cm_mmc=Google%20Base-_-Adhesives,%20Sealants%20and%20Tape-_-Thread%20and%20Gasket%20Sealants-_-2TRL1

[Itzkwik]

I've had good luck with Rectorseal. Should be available at Lowes/Home Depot.

[nissan_crawler]

I've had good luck with Rectorseal. Should be available at Lowes/Home Depot.

I'm with this guy.

[mears]

I've had good luck with Rectorseal. Should be available at Lowes/Home Depot.

The two 125PSI sealants are made by RectorSeal.

The pipe joint compound is made by Oatey: http://www.oatey.com/Plumber/Shared/ProductGroupDetail/90/Great+White%E2%84%A2+Pipe+Joint+Compound+with+PTFE .html

Here are the two different RectorSeal sealants they carried:
http://www.rectorseal.com/index.php?site_id=1&product_id=215
http://www.rectorseal.com/index.php?site_id=1&product_id=218

[kbs2244]

Are you sure it is a thread leak?
It may be a hole in the casting.
Sometimes it is easier to just replace the valve.
I have seen the threads cut too deep and they will never seal since they are under sized for the hole.

[buening]

The Oatey pipe joint compound is what I used when I plumbed my air compressor lines (3/4" iron pipe) and have had good luck with the stuff.

[Jokeman]

I use Permatex Thread Sealant.