I am constantly arguing with my coworkers about putting pipe dope on unions and I was wondering what other plumbers are thinking or doing. Please help solve (or contribute) to this argument.
My View:
First I do not believe in putting pipe dope (tape or liquid) on unions if they do not need it. I will tighten the union first without any dope if does not leak-- great leave it alone. From my personal experience this works on most of the unions I have installed. If the union still leaks after reasonable tightening I will break it and smear a little bit of liquid pipe dope on the face of the union where the contact is made and retighten. This usually takes care of the problem. If the union still leaks I would (I say would because I have never actually had too) wrap the threads with three layers of Teflon tape and smear more pipe dope on the face of the fittings and retighten.
My Supervisor's View:
Do not smear pipe dope on the face of the union but wrap the threads and everything else with about twenty layers of Teflon tape and then tighten the union with an oversized pipe wrench. The Teflon tape will create a diaphragm around the sealing part of the union that will prevent it from leaking.
My Lead-man's View:
Put liquid pipe dope on the threads always because when you tighten the union it creates frictions and the pipe dope lets if move easier and allows you make a tighter connections. He even uses it on dielectric unions and angle stop to flex connecter where there is a rubber gasket that seals the joint.
My Co-worker's View:
Dope everything-- it can't hurt can it?
I feel that if it is the metal on metal contact of the two faces of the union that actually makes the union seal and not the threaded part of the union so why would you need any pipe dope at all on the threads. And even though I believe that there is friction when two metals are moving while in contact I do not think it has any effect on whether the joint will leak or not. If you do not use pipe dope when connecting your TurboTourch to your B-tank why would you use it in your piping system for similar connections. What I believe is that there needs to be a clean uninterrupted surface on both sides of the union and making a solid but not overly tight connection.
What are your thoughts or comment?