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Thread: Plastic to plastic threaded fittings... use teflon or not?

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  1. #1
    DIY Senior Member DavidTu's Avatar
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    Default Plastic to plastic threaded fittings... use teflon or not?

    On a boat's fresh water system I had to replace a threaded hose fitting. I put on teflon tape thinking it would help seal better but no matter how tight I screwed the fittings together I still get drips. Now I am wondering if w/ plastic to plastic threaded fitting connectors, is using teflon causing the problem? (Any other ideas why it'd still leak?--it cannot be further tightened)

  2. #2
    Plumber jimbo's Avatar
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    One to two wraps max of tape is ok. Main cause of leakage on plastic threads is overtightening. Hand tight plus one/half to one full turn...that's it. You have proabably already distorted the threads.

  3. #3
    Moderator & Master Plumber hj's Avatar
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    quote; Hand tight plus one/half to one full turn...that's it.

    I have never seen a plastic thread NOT leak if that procedure was followed. I tighten them until they are TIGHT, regardless of how many turns it takes.

  4. #4
    DIY Member RinconVTR's Avatar
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    Not using tape will not only allow leaks, but it can also "weld" the plastic together making disassembly almost impossible.

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    This type of thread is tapered and interference...to seal between the threads, you MUST use something, either tape or a pipe dope rated for use on the plastic pipe you have. Under an ideal world, 1/2-turn after finger tight MIGHT work, but don't count on it.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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