how tight to tighten a 1in union

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by rrekih, Nov 29, 2009.

  1. rrekih

    rrekih New Member

    Messages:
    46
    Location:
    Canada
    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?
  2. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Are you using any dope?
  3. Basement_Lurker

    Basement_Lurker One who lurks

    Messages:
    668
    Location:
    Victoria, BC
    If he is, I'm sure he only puffs, and does not inhale
  4. Doherty Plumbing

    Doherty Plumbing Journeyman & Gas Fitter

    Messages:
    810
    Location:
    Penticton, BC
    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. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,815
    Location:
    Cave Creek, Arizona
    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 a moderator: Nov 30, 2009
  6. rrekih

    rrekih New Member

    Messages:
    46
    Location:
    Canada
    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. Terry

    Terry Administrator Staff Member

    Messages:
    15,121
    Location:
    Bothell, Washington
    I don't use dope on the face of the union.
  8. rrekih

    rrekih New Member

    Messages:
    46
    Location:
    Canada
    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. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,815
    Location:
    Cave Creek, Arizona
    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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