I am in the process of repairing PVC pipe, which was broken due to freezing. I'll be connecting the PVC pipe to a metal check valve. Should I use Teflon tape or pipe dope when connecting PVC to metal?

  • Could you provide dimensions of the PVC and Copper in question? Commented Mar 18, 2015 at 12:41
  • 1
    possible duplicate.
    – Tester101
    Commented Mar 18, 2015 at 13:48
  • Agreed. That appears to be a duplicate. Commented Mar 18, 2015 at 13:57
  • I concur, however this answer has a picture of the new 'blue' stuff, which seems better than oldschool Teflon, but my can isn't old enough yet to make that call.
    – Mazura
    Commented Jul 17, 2015 at 1:30

2 Answers 2


This is what my plumbing supply house sold me to attach a 3 inch PVC threaded fitting into cast iron pipe.

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My personal preference is pipe dope instead of Teflon tape every time unless doing low pressure flared tubing. Teflon tape only works if applied properly and that seems to be an issue a lot of the times. Pipe dope you coat the threads and it fills in the areas as you tighten. Yes it can be messy but having to go back because of a leak can be very costly. Coat the threads of the pipe not inside the fitting and wipe off any excess. I have installed and repaired air, water and gas piping for the last 20+ years and have found that the majority of the leaks issues have been Teflon tape installed incorrectly.

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