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Thread: how tight to tighten a 1in union

  1. #1
    DIY Member rrekih's Avatar
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    Default how tight to tighten a 1in union

    How tight should a 1in copper union be tightened?
    I have 2 that I have tried to tighten to no avail.
    Still very small leak under air pressure test of 40psi.
    I did sweat a threaded adapter to the union.
    The seal looks clean but dis-colored.
    Is there a way to lap the two matting surface's together?

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    DIY Senior Member dlarrivee's Avatar
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    Are you using any dope?

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    One who lurks Basement_Lurker's Avatar
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    If he is, I'm sure he only puffs, and does not inhale
    Broken promises don't upset me. I just think, why did they believe me? -Jack Handy


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    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by dlarrivee View Post
    Are you using any dope?
    You aren't allowed to use pipe dope on the mating surfaces of a union.

    Sand each surface lightly with some land cloth and don't be afraid to crank the union really tight.

  5. #5
    Moderator & Master Plumber hj's Avatar
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    Default union

    quote; You aren't allowed to use pipe dope on the mating surfaces of a union.
    Now you tell me, after 60 years of doing it. Put dope on the union's faces and the thread for the nut, then tighten it as much as you can. You will not, and cannot, "overtighten" it. Unless you use such huge wrenches that you snap the nut, but that would be VERY hard to do.
    Last edited by Terry; 11-30-2009 at 07:58 AM.

  6. #6
    DIY Member rrekih's Avatar
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    Dam I just thought dope was for doper's.
    I guess I will get to try some soon.
    But I promise not to inhale.
    At least not to much.

    I did use a 14in approx. wrench and did reef on it pretty good.
    There we go with the dope thing again. "reef"

  7. #7
    Forum Admin, Expert Plumber Terry's Avatar
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    I don't use dope on the face of the union.

  8. #8
    DIY Member rrekih's Avatar
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    So some don't some do.
    I am sure if you looked at the manufactures spec. for the union it would state not using pipe dope, probably even give a torque setting.
    I understand the theory behind the union with the flange being the seal point.
    A question, the 2 mating surface's look at lot like the valve and seat in a engine. So in theory if I used a lapping compound and lapped the 2 together I should get a proper seal.

  9. #9
    Moderator & Master Plumber hj's Avatar
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    Default union

    They were lapped at the factory. Your problem is that you are using A 14" wrench, you need TWO 14 inch wrenchES, so you can tighten the nut while resisting on the other piece.

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