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Thread: Leaking Dielectric

  1. #1

    Default Leaking Dielectric

    I recently extended a preexisting line of galvanized cold water to feed what will become a half bath in my basement.

    I used copper for the new run. I joined the copper and galvanized with a dielectric union, as advised by many.

    Everything seemed to be great and all the joints, turns, Ts, etc.

    The only part that is a problem is the dielectric union itself. The union is leaking at an extraordinarily slow rate on the galvanized side. Inside of 8 hours, the leak will produce a drop of water. I used joint compound on the female threads and tape on the galvanized male end.

  2. #2
    Moderator & Master Plumber hj's Avatar
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    Aug 2004
    Cave Creek, Arizona

    Default dielectric

    I would revise that to say "advised by a few", because "many" of us have absolutely no use for dielectric unions, because they are mainly cosmetic to please an inspector, but have little, if any, value in the system. You may have a bad pipe thread. Sometimes the pipe rusts through where the pipe is thinnest at the thread, but does not leak until it is disturbed and a new fitting is attached.

  3. #3
    DIY Senior Member WV Hillbilly's Avatar
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    Aug 2008


    Sometimes those type of leaks will seal themselves & maybe just a little more tightening would solve the problem .

  4. #4
    Master Plumber master plumber mark's Avatar
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    Feb 2005
    indianapolis indiana - land of the free, home of the brave....
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    Talking leave it alone

    Dialectric unions are a waste of time

    also, I agree that you should leave it alone fo a week
    or two, and the leak might just stop itself...

  5. #5


    Thank you for the feedback! I will let it sit.

    If I had to do it over again, the union would be scrapped. As it is, if it continues to seep (the amount of water is seriously small) would you think I would be best served removing the union and putting a coupling of some type without a dielectric?

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