Pipe dope on union mating surfaces?
Posted by DavidH on April 20, 19100 at 07:20:22:
I (a civilian) got a lecture from an experienced plumber the other day that the proper procedure for using copper unions was to apply pipe dope to the WHOLE fiting - threads, friction surface (where nut turns) AND on the mating surfaces.

Being a civilian, I had never used pipe dope on a union, and in particular, felt that the the nature of soft metal would have the union seal better with no dope on the mating surfaces.

So, what is good practice with unions? Is there an definitive reference on this in some plumbing standards manual?

Just curious.

David



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