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Thread: Leaking Brass Union

  1. #1
    DIY Junior Member proxybox's Avatar
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    Default Leaking Brass Union

    Hi, I have a Grundfos recirculating pump that I installed this weekend. I installed brass unions on each side in the event that I have to remove the assembly for repair in the future. Everything works fine, but one of the two brass unions (brand new) that I installed is leaking. I tried tightening it down further, but with no luck. I noticed that the angle of one of the pipes approaching is at a slightly different angle that the pump side. How much tolerance is there for keeping the two sides (flare to other side) perfectly straight? I'm assuming that the connection has to fit exactly for the fit to work properly.

    Was the proper installation method to assemble the two unions to the pump, tighten the unions and then solder the sweat ends of the union into my piping system? I soldered the sweat ends first with the unions 'loose' and then tightened them down.


    Thanks,

    Jonathan

  2. #2
    Plumber RioHyde's Avatar
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    Default

    First make sure that you didnt get solder on the union where the seal is made. If everything is clear of debris, including any solder drips, spots or errors, try putting a little pipe dope on the part that makes the seal (the "flared" part, not the threads).

  3. #3
    In the Trades Gary Swart's Avatar
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    Default

    I'm a little concerned about the angle you mentioned. As you know, the union must seat in order to make a seal. The theads are to pull the male and female ends together and not to form the seal. That is not to say the theads don't have a sealing function, but if the male and female ends are cocked, then you won't have a seal. The pipes should be very close to level so that the union doesn't have to force the ends to seat. I like to screw a union together with my hands to the point that it only takes a small amount of wrench tightening to finish.

  4. #4
    DIY Junior Member proxybox's Avatar
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    Default I figured it out

    I unsoldered the joints, reassembled the unions and tightened them down. Once I had everything screwed up, I soldered the entire assembly back in. No leaks. I guess you really have to have the flare and union part lined up exactly. The solder joints, on the other hand, have a little more play.

    thanks for all the help.

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