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Thread: Leaking Compression Union - SOS!

  1. #1

    Question Leaking Compression Union - SOS!

    Greetings! I'm not quite an expert here so please excuse me up front if I don't have the terminology just right. I recently installed a full-house water filter, which required me to use a reducing compression union from 1" s-steel to 3/4" copper. Unfortunately, I continue to get a very slow drip from the the end of the compression union. The leak is located on the copper side of the union right behind the nut. It is not coming from the threaded portion of the union. I'm good there. I've replaced the washer inside the nut twice and I continue to get the leak. Does anyone have any suggestions? Are there compounds or sealants I should use? Please help! Thank you.

  2. #2
    DIY Senior Member Mike Swearingen's Avatar
    Join Date
    Jan 2005
    On Albemarle Sound In Northeastern NC


    A compression fitting seals with the ferrule ring.
    Either wrap a wrap of teflon tape or smear a little clear silicone caulk on the ferrule ring to seal it. The compression nut threads won't seal it, just the ferrule.
    Good Luck!

  3. #3

    Default Leaking Compression Union - SOS!

    Thanks Mike. I agree that the leak is hapening at the ferrule. Does it matter that the ferrule is plastic? Basically, the end of the coper pipe is flanged with a nut over the ferrule and washer. This is the washer I've replaced two times. So are you suggesting I just apply some silicone to the ferrule? How does that help stop the leak (just curious)?

    Also, I should have mentioned that in my previous two attempts, the washers that I used were already pre-coated with a greasy material. Not sure if it was silicone or not. But they were coated and I'm still getting my drip. Are there any other coatings that would make my seal "leak-proof"? I friend mentioned trying Permaseal, but I thought that was used for automotive engine applications.

    Thanks to anyone who can help!


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