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Thread: Leaking in-wall lav faucet valve

  1. #1
    DIY Junior Member oddjob's Avatar
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    Default Leaking in-wall lav faucet valve

    I bought a single handle wall mounted faucet for a new bathroom addition. The inlets on the mixer are female. I hooked them up to pex tubing with NPT 1/2" male threaded to 1/2" pex crimp fittings. The threads were treated with pipe dope (Rector Seal #5).

    The system is now leaking from the threaded connections. I think the male fittings may be bottoming out in the mixer body threads before establishing a seal.

    Am I using the wrong kind of fittings?

    Thanks for any input.

  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    Can you post an instruction sheet or picture?

    If they are tapered threads, then the pipe dope would be fine.
    If they are straight cut threads, they may use a flat rubber washer in between.

    But I'm only guessing without a picture.

  3. #3
    DIY Junior Member oddjob's Avatar
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    The item came without instructions (risks of ordering from online discounters) and the specs from the manufacturer's web site don't say what standard the threads are.

    I'll try the washers to see if that seals things up.

    Is it acceptable practice to use rubber washers behind the wall where there won't be maintenance access?

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    Forum Admin, Expert Plumber Terry's Avatar
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    It's easy enough to tell if the threads are tapered by looking.
    If they are tapered, then you can't use a rubber washer.
    You might just need to tighten things up.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    If they came with washers, then the threads are very likely not NPT (tapered) and the seal is created by the washer, not in the threads and pipe dope (or tape). You'd need a different connector.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #6
    Moderator & Master Plumber hj's Avatar
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    The valve WILL have tapered pipe threads. Any "odd" thread will be the PEX adapters, although even they should have the correct threads. You probably did not tighten them properly. Did you follow someone's directions to tighten them hand tight and then an additional turn? If so, that is your problem. You cannot tighten threads to a formula.

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    Plumber Winslow's Avatar
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    Quote Originally Posted by oddjob View Post
    I bought a single handle wall mounted faucet for a new bathroom addition. The inlets on the mixer are female. I hooked them up to pex tubing with NPT 1/2" male threaded to 1/2" pex crimp fittings. The threads were treated with pipe dope (Rector Seal #5).

    The system is now leaking from the threaded connections. I think the male fittings may be bottoming out in the mixer body threads before establishing a seal.

    Am I using the wrong kind of fittings?

    Thanks for any input.
    If you bottomed out the threads then you either over tightened them or they are not tapered threads. I have run into that on european faucets. If you can hand tighten them all the way in then the threads are not tapered. I use loctite in that situation and it works well.

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