any of you guys know what kind of sealant to use on 150psi air compressor threads and fittings. I read on the internet(bad idea) to use joint compound instead of tape. As you can see, it leaks. I tried teflon tape also and it leaked.

 

When I plumbed my Quincy QT5 I used 3/4" black pipe which handles 175 psi between the tank and regulators. I used same stuff you have pictured and it doesn't leak. Mine, come to think, might have been the compound that has Teflon in it. I hate Teflon tape. Stu

 

Pipe plugs have tapered threads, so they need some kind of sealer, whether it's tape or paste, and then tightened good. You might try a different plug. You may have a burr or bad threads on the plug or fitting that's not letting the plug tighten properly.

 

Are you talking about the little bubbles on the joint? That's a pitiful small leak, will probably corrode and plug itself in no time. I would agree the plug likely has poorly cut threads.

 

If you have leaks that pipe dope or tape won't seal, you have bigger problems than the sealant.

Brad

 

You are right to not use Teflon tape. Teflon tape is an excellent thread lube but a poor sealant plus it invariably gets into your controls and fouls them up.
You can't go wrong with locktite pipe dope. It flows during makeup but once oxygen is excluded it hardens, takes anywhere from 5 minutes to 1/2 hour to set.
People usually don't understand the dynamics of leaks at pipe threads. Pipe threads are tapered. That is the "T" in NPT, national pipe tapered. In order for the fluid to leak through the thread it must follow the thread all the way up in the root diameter of the thread. If you break that path at only one spot along its path you have stopped the leak.
Non hardening dopes can get blown out of the threads at pressures higher than about 50 psi.

 

the plug was just a test. It was a new plug and the threads looked ok. I have to run about 25 feet of pipe, elbows, valves and such so I want to makes sure it holds before I take the time to build the whole thing. That small leak as you call it dropped 10psi in about 5 minutes. Is it unrealistic to have a system that is leak proof. ie after a week or so do you guys have to pump up your air compressors.

 

If you bleed the tank daily as you should you will have it kick on to build back up for that reason if no other. I've had more issues with China junk hose end leakage than pipe issues. Also had to rebuild my Reelcraft overhead reel last week because of leakage. Stu

 

I don't know if I'd go so far as to say unrealistic, because theoretically you should be able to build a system that doesn't leak. After all, they can do it with natural gas systems. But in all the shops I've worked in over the years, and there's been quite a few, I've never been in one that didn't have the little background hiss of an air leak somewhere. If you think about the number of fittings and connections in an air line system, hard lines, hoses, couplers and connectors, tools, etc., it's highly unlikely you'll ever have one that seals perfectly.

 

Use copper pipe with sweated fittings and valves. I suspect the 10 psi loss in 5 minutes was due to the air in the tank cooling down, unless your compressor has an aftercooler.

 

This may not be for everyone but..... I have used JB weld for pipe dope on several occassions in extreme cases. When nothing else would do the job. Hope this helps.

 

Me too. I feed my barn with an underground line from the shop with air drops on both sides of the barn. I JB'd the joints of the 40' overhead that is 15' off the floor. Never worried about it afterward. Stu

 

I have quite a few lines from my compressor all feeding from the outlet where I have a ball valve. When I am not using the air I just close the ball valve. If I have a hose or two hooked up to any tool (impact, nail gun, etc.) they wont have air in them about an hour or so later because of the quick disconnect ends. Other than that I have no leaks and I used Thread Sealant with PTFE (Polytetrafluoroethylene) which works really well.

 

Those threads are tapered. If the threads on the hole are too big or the threads on the plug are to small, no amount of thread sealant will solve your problem. Speaking of hole threads being to big, did I ever tell you about the girlfriend I had in the Arny?

Brad