I was over at a friend’s house this weekend that he bought recently. He asked me to take a look at a bit of pluming that he said was “corroded, with rusty drops of waterâ€. Upon taking a look at the three quarter inch threaded copper pipe I noticed a rusty drop of water dripping from a corroded T-connection. Instead of a copper elbow at this bend there is a copper T connector, and plugging the “Tâ€, there looks to be a galvanized plug. I told him that two dissimilar metals should never be put together, that they will corrode each other. My question to you all is, can I replace just the plug with a copper plug or do I have to replace both the T and plug? The T is copper but is discolored to a whitish color. The plug and T were sealed with plumbers dope, not Teflon tape. For my own curiosity, if Teflon tape were used instead, would the connection have rusted also? With Teflon, wouldn’t the two pieces be out of direct contact, thereby preventing the corrosion process? Thanks for all your advice and help.
Replies
I assume the connection is threaded and the galvanized plug is screwed into a copper fitting? If so, yes, you can just replace the galvanized plug with a brass one, so long as the threads are not mangled.
They don't make copper plugs. Brass is completely compatible with copper and is what should have been used rather than galvanized steel.
Even with tape or pipe dope, somewhere in the threaded connection there would be metal to metal contact. When a threaded fitting is tightened, the tape or dope is squeezed out until there is enough metal touching that the connection no longer turns easily and the joint feels properly tightened. Since it's difficult to mass produce threads so precisely that there is metal to metal contact all the way around without the tiniest hole, dope or tape is used to seal the very tiny passages that often are present even after a joint is screwed together tightly. In your friend's case, the plug would have corroded if either tape or dope had been used.