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Thread: Connecting Plastic Fittings to Copper

  1. #1
    DIY Member tonyn1's Avatar
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    Default Connecting Plastic Fittings to Copper

    I'm just installing a water softener which has a plastic, which I believe is nylon, valve. I ran 3/4 copper lines down to it on which I installed a 3/4 x 1" threaded female copper fittings. I put teflon tape on the male plastic fittings and installed. When I turned the water back on, I noticed some drips coming out of the connection. I tightened the fittings some, careful not to over tighten and break the plastic fittings. Checked again and still had some leakage so I went to pipe sealant and thought I had it licked, but I still have a very small amount of leakage. I don't want to tighten more as I'm afraid I might break the plastic fittings. Suggestions?

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    Jack of all trades frenchie's Avatar
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    There's not a rubber washer involved in this assembly, is there? If there is, you oughtn't use teflon.

    Oustide of that possiblity... I got nothing.

    Wait for the pros...
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  3. #3
    DIY Member tonyn1's Avatar
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    Default

    No rubber involved.

  4. #4
    Jack of all trades frenchie's Avatar
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    The pros will be along shortly.
    Master Plumber Mark:

    there is nothing better than the
    manly smell of WD 40 in the air
    while banging away on brass with a chisel and hammer...

    it smells like......victory......

    do not hit your thumb...
    __________________
    Just so everyone's clear: I'm the POODLE in the picture ("french", get it?) The hot woman is my wife.

  5. #5
    DIY Member tonyn1's Avatar
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    Where are they? Still waiting.

  6. #6
    DIY Member msgale's Avatar
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    Default cannot use adapter to join copper and plastic

    they expand at different rates,
    Also, if the female plastic is overtightened it willsplit at an inopportune time.

    you need a compression fitting, one side copper ferrule to over copper tube, other side plastic ferrule to go over a pvc or cpvc tube. then each is tightened, and it will not leak ever.

    or, there are transition fittings that use rubber washers, for connecting metal to plastic.

  7. #7
    Forum Admin, Expert Plumber Terry's Avatar
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    Default

    If you have a plastic male adapter going into a female copper fitting, and you have used Teflon Tape, it should work if it's tight enough.
    Sometimes plumbers use a little thread sealant over the Teflon tape too.

    It sounds like you are doing the right thing.
    It's hard to tell someone how tight to do these thing though.
    My tight, may be different from your tight.

  8. #8

    Default

    A lot of softeners come with a special nut that fits on the plastic thread and has a copper stub that needs to be soldered to. If you had that type, the thread would no be tapered and would not be designed for a threaded fitting.


  9. #9
    DIY Member tonyn1's Avatar
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    I don't have the type of fittings you are talking about. However, I did solve my problem. I think the problem was I was using a cheap grade of teflon tape. It was too thin and was getting torn up when I screwed the fitting in. I found some "Blue Monster" brand that is a bluish color and advertised as professional density. I made sure I put plenty on and then applied a thin coat of sealant also. It seems to have done the trick. Thanks everybody for the help.

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