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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

Luiz Borges
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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) – RedGrittyBrick Dec 30 '15 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 – Luiz Borges Dec 30 '15 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. – BrownRedHawk Dec 30 '15 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? – Luiz Borges Dec 30 '15 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. – BrownRedHawk Dec 30 '15 at 14:22
  • Visually they look tapered, but I don't think that it tightens enough. Also another fitting that I tried seem to "bottom out". I will buy the dope and use it instead. – Luiz Borges Dec 30 '15 at 14:24
  • @BrownRedHawk Just got the dope, it is very sticky and you are supposed to put it in both male and female threads, wait 3 minutes and then join the pieces. I made a test and will check if it is flexible after curing. – Luiz Borges Dec 30 '15 at 16:41

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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.

Ed Beal
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