I'm practicing some connections on water lines, but I'm a bit worried the parts I have are bad.

nipple fully threaded

Here I finger tight the parts and then was able to do just a half turn with the channel lock before felling like it was "right". I'm not sure if that was enough or if I hit the "neck" of the male threads.

Below I show how the tape got after that, in the left side I used 15 turns of tape and on the right side just 5 turns. Both were cut around the last thread, does that indicate that the seal was done? How much tape is enough?

taped nipple

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    The PTFE tape just has to seal around the circumference, it shouldn't matter if a small part of the threads cut the tape. In the past I've rarely used more than about 5 turns. The real test is to pressurize your connection and check for leaks. I much prefer compression fittings - much less messing around (other than to clean the pipe a little) Dec 30, 2015 at 12:47
  • I using PVC and CPVC so I just need to make those connection on 2 shower mixers, 10 connections total, and I never had good experiences with threaded connections Dec 30, 2015 at 13:09
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    As per @Ecnerwal (whom I do trust) says these fittings do have a leak path. I'm not sure that PTFE tape is the 'right stuff' to seal this path. I think that some kind of dope or similar might ultimately do a better job that ptfe tape. Dec 30, 2015 at 14:15
  • The only dope I could find here is one based on solvents and some kind of rubber copolymer that semi hardens and is flexible after curing. I'm supposed to apply wait 3 minutes and join the connections. I couldn't find any with PTFE. Do you think this works? Dec 30, 2015 at 14:19
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    That sounds like it might be the correct stuff. If they are tapered pipe threads, you would only need about 3 wraps with tape. If they are non-tapered threads, dope is the way to go. It hardens and prevents passage of materials through the threads. Dec 30, 2015 at 14:22

1 Answer 1


Luiz, to me this looks like it is not sealing and the pipe Dope liquid really doesn’t do much better than PFTE tape. I have had better luck staying with plastic 100% or metal 100% until the final fitting used to connect the shutoff valve. The PFTE tape should be “chewed up” when you put on the fitting, if not the 2 different sizes are not sealing and may very well leak. I have seen this same thing when folks use electrical couplings for pipe (they are not tapered like normal pipe couplings) and they started leaking after the walls were closed.

  • Those are metal to metal. The blue PVC pipe has female brass treads in it. Dec 30, 2015 at 14:56
  • They are only chewing one and a half turns, I don't think it is enough. I mentioned in a comment above a pipe dope that is solvent based and cures semi hard yet flexible. I think it should work better. Dec 30, 2015 at 14:59
  • I would be cautions it looks like the male is undersized or female is oversized or not tapered with the metal to metal they should much tighter.
    – Ed Beal
    Dec 30, 2015 at 15:01
  • I don't have much choice, this is what is available here in Brazil? Dec 30, 2015 at 15:02
  • Metal to metal, you should get more than one turn's worth of tape cutting. Feb 28, 2016 at 16:47

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