3/4" Copper UNION - Use Teflon Tape or Pipe Dope?

The threads on a union play no part whatever in the sealing function, they are there solely to enable the sealing surfaces
to be pulled tightly together. No dope, no tape, no nuttin'.
 
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Although nothing is required on ANY part of a union joint, I like a little non-setting paste like Great White, both on the threads and very lightly on the mating surfaces, just as a lube and protector. It works for me! Many will suggest a little coating of light oil.
 
kreemoweet said:
The threads on a union play no part whatever in the sealing function, they are there solely to enable the sealing surfaces
to be pulled tightly together. No dope, no tape, no nuttin'.
Click to expand...

Pipe dope on the threads would be used as just a lubricant. Not to seal anything.
 
Pipe dope on the two mating faces will compensate for any minor irregularities. On the threads it helps them tighten easier. Putting it on the surfaces BEFORE soldering, makes them "dirty" so the solder does not adhere to the brass, which helps in a vertical installation.
 
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These are 1/2" unions for American Standard tub valves. They didn't seal dry. Rectorseal 5 on the face and threads worked.
hj, I remembered your advice on this one.


lee_02.jpg
 
hj said:
An 18" pipe wrench might be a helpful accessory.
Click to expand...

The day I need an 18" wrench on 1/2" pipe, I'll let you know.
My biggest worry on those things is stripping the brass theads completly off.
Which I have done on 3/4 unions.
 
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I had a 1" sweat union I installed about 2 weeks ago, and I DID use an 18" wrench to tighten it. Last night the customer called and said it was leaking. It had loosened somehow and even though I tightened it at least one more turn it would not stop dripping so I took it apart and put pipe dope on the faces and tightened it again WITH an 18" wrench.
 
hj said:
I was more worried about the nut cracking from the pressure. If it happens again I will put an "O" ring between the pieces.
Click to expand...
hj said:
I had a 1" sweat union I installed about 2 weeks ago, and I DID use an 18" wrench to tighten it. Last night the customer called and said it was leaking. It had loosened somehow and even though I tightened it at least one more turn it would not stop dripping so I took it apart and put pipe dope on the faces and tightened it again WITH an 18" wrench.
Click to expand...
 
Looks like my gun went off half cocked, trying to post a comment.

Anyway, I bought a 24" aluminum pipe wrench maybe a year ago. I got it for one reason and one reason only:
it was half price. I bring it out maybe once a month and I'll tell you what, when I put it on something it moves.

I'm with the woot tranny on this one. A big wrench can make all the difference in the right place.
 
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