I have tried 3 turns, lots of turns , less turns, I do it the right way I am like 100% sure but I always get leaks, I use it for fittings in compressed air (8 bar) https://www.youtube.com/watch?v=C0kBeMNfWx8

I do it how the guy teached in this video. What do I do?

  • Why type of fittings and what color PTFE tape? When you face the end of the pipe, which way are you wrapping the tape? How far do you tighten the fittings? – Hari Ganti Mar 3 '17 at 23:20
  • 3/8" NPT, I use white PTFE tape which I bought at hardware store (called plumbers tape). What do you mean by "When you face the end of the pipe, which way are you wrapping the tape?" I am pretty sure I am doing the right direction – Diogo Mar 3 '17 at 23:22
  • I tighten them most of the way or all the way but it always leaks, I have tried everything. – Diogo Mar 3 '17 at 23:23
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    First, different colored PTFE tapes are meant for different purposes. Yellow is for gas sealing (natural gas, but I am not sure that is as relevant). Also, I am asking which way you wrap because "I am pretty sure I am doing it the right direction" doesn't tell us if you actually are doing it right. Tape some pipe, look down the length of it with the threaded end near you. When you wrap the tape, which way do you wrap it? As for fastening, how many threads can you see when the fittings are tightened down? Can you see any threads? – Hari Ganti Mar 3 '17 at 23:27
  • Better yet, take a picture of the pipe and the fitting before you do anything, after you wrap the threads, and after you seat them, then upload those. – Hari Ganti Mar 3 '17 at 23:29

I think some modern NPT threads are not as well made as in the past. I have had more leaks than decades ago. Used to be white Teflon tape would work every time, but the last four (recent) 1/2" and 3/4" NPT connections I have made leaked.

In both cases I had to take them apart and use pipe dope. One (washing machine supply valves hot and cold) seeped for days but finally sealed, another (outside faucets) had a serious seep and may or may not have stopped (outside and not a problem). First application of pipe dope didn't work; I took it apart again and this time used pipe dope on female as well as male threads. The water meter shows no observable leak.

  • Some people on this site have reported that they use, or sometimes use, both Teflon tape and pipe dope. I don't know what the order of application would be. I always thought the proper procedure was that pipe dope was applied only to the male threads so that excess dope would be squeezed out of the pipe as the threading progresses, but on my outside faucets I gave up and put dope on the female threads too. This produced a marked decrease in the seep rate. I have insulation on these two faucets and can't see the completeness of the seal without removing it. – Jim Stewart Mar 4 '17 at 10:29

Wrap the teflon tape onto the threads in same direction as if you were screwing on a fitting. Looking at the pipe with the fitting threads on in a clockwise direction, wrap tape around pipe towards the right (clockwise) and give it 4-5 turns minimum. But, you can put 10-20 if you want as long as you can get the fitting started. I have never had any trouble myself. But, you can also put pipe dope on before tape and after as well and then you can't possibly have a leak. If you do...well then I recommend trying your hand at working with wood instead and have your cat do all pipe work from here on. Good luck bud.

  • I always do this but I still have leaks, I try spraying soapy water and it starts bubbling – Diogo Mar 4 '17 at 21:06
  • I thought we were talking about water pipes, my mistake. I suppose that there is no joint paste used for compressed air connections, right? I know that there are manufacturers of threaded brass pipe and fittings who claim that their products don't have the helical leak path of ordinary products. It is possible that the OP is trying to seal sub-optimal threaded joints? – Jim Stewart Mar 4 '17 at 21:30
  • I am using 3/8" npt threaded fittings which I bought at hardware store – Diogo Mar 4 '17 at 21:35

When using teflon tape, you only need 3-4 wraps put on in the same direction as you turn on the fitting. Start the wrap, at the end of the fitting and wrap towards the piping keeping the tape tight, "it takes practice". Then, you can add some pipe dope on top of the teflon tape,(it doesn't have to be expensive dope). Or you can forgo the teflon tape and dope and just use RTV silicone , red, clear black , or whatever color you want. I used the silicone on air, water, nat gas ,fuel oil , almost anything, and give it time to set up. I even used it on steam and hot water boilers and piping if I was dealing with questionable pipe threads. One caveat, if the threads are really crap, like some foreign stuff throw the stuff away and by American.


If you're an occasional DIY plumber like me, use dope. (I used Oatey Pro Dope from Home Depot but I'm sure it's nothing special.) Cover the threads completely on the male fitting. Tighten with opposing wrenches until it feels like you'll break it pushing harder. If you don't have that feel, use maybe 6" long wrenches for a 1/4" fitting, 12" wrenches on a 1/2", and big pipe wrenches on bigger - then tighten until you can't really put more force into it. Of course if orientation is key, try to get at least one full wrench turn and then more to orient.

I built an all lead-free brass well tank tee with four different NPT sizes, and I found that I needed pipe wrenches for the 1/2" and bigger. A pipe wrench is made to dig in and grip tighter with more force. Open-end or adjustable wrenches just slip. Luckily I inherited 3 pipe wrenches from a grandfather so I had what I needed.

I got 100% leak tight mating with dope and no additional tightening after pressurizing. That was my second try. First try I used thin teflon tape and got 100% LEAKING even tightening more than I felt comfortable. The dope was easy and did the job.


Loctite 567 3/8 1/4 fittings are difficult with t tape Sonia use 567 no tape

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    Please use complete sentences with punctuation (and complete words) in your answer. It's very difficult to interpret this. – isherwood Jun 23 '18 at 13:19

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