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I've never built with pipes before so maybe I'd need some general advice regarding leakage. On a specific note, I've built a system (see picture) where it leaks practically everywhere. I've sealed it with NASTRO P.T.F.E tape on some places where it seems to work. I've screwed the pipe parts very hard so it shouldn't leak but it does.. a lot. It seems unreasonable that I need to use NASTRO tape everywhere. How do professionals do it? My bathrooom pipes doesn't have any tape, what are they doing differently?

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Edit (25th of march):

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    What pressures are you working with? Trying to seal for 140psi is a heck of a lot different that trying to seal for 500psi – BrownRedHawk Feb 23 '16 at 13:42
  • not more than 5 bar, 70-80 psi – Lennart Feb 23 '16 at 13:55
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    Looking at your fittings you may have a mix of straight and tapered threads. The size and thread pitch are the same but it is almost impossible to get a straight thread / taper thread combination to seal. – Ed Beal Feb 23 '16 at 13:57
  • so whats the solution, u think? cover it all up with tape? – Lennart Feb 23 '16 at 14:22
  • Are the fittings you used for aesthetics, or are those the only fittings available to you? Why are you so against using PTFE tape on all the joints? – Tester101 Feb 23 '16 at 19:10
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Hold the tape in your left hand – to avoid running it the wrong way and having it unravel as you start threading.

If you can bottom-out four adapters into each other, they're likely all the right thread type, you just didn't use enough tape. IME, warping it three times is sufficient. On fittings that don't like to cooperate, you may need substantially more to make the seal.

When applying the tape, you should only stretch it with enough pressure to let it sink into the threads. If you pull any harder, you'll cheat the depth of the wrap. Finish it by seating it well with your thumb or rolling it in your palm.


I see in the picture only a pair of pliers and no crescent wrench or pipe wrench. I'd have said that was your problem, except that you somehow managed to bottom-out those fittings, so my vote is they're just loosey-goosey. Note, with enough tape on them to seal and without the proper wrench, you might never get it airtight.

I don't bother to pressure test a fitting that BOs, I already know it's going to leak. I just take it apart and:

Use more tape.

When you pipe-fit, you're looking for the tension to become progressively stronger (to the unexplainable point that has ever been expressed to me as, "that's good"; it only comes via experience), if it all of a sudden stops, you're likely in trouble.

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Imagine standing to the left of the photo. Hold the pipe in your right hand and the tape in your left, and it's basically impossible to do it the wrong way. It is recommended, as shown above, not to cover the first two threads but I do anyway. Having built up a good wrap at the rear threads, I'd finish it off with a warp or two around the starter threads, so that it looks like this:

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  • Oh so the tape is applied on the threads, that means id have to leave the adapters not fully tightened, right? – Lennart Mar 26 '16 at 18:16
  • @Lennart - The right amount of tape on the threads will make it "snug up" way before the fittings bottom out. "Sufficiently tightened" is snug: feels 'good'. Unless you're using a three foot pipe wrench (way too long for this work) you'll feel when it's good enough. See the edit for more about tape, and the pipe-fit link for how to "back up" your work (use two wrenches). – Mazura Mar 26 '16 at 22:59
  • But I prefer pipe dope Vs. tape anyway. Only when I need it to not "spread and be pushed out of the way" do I use tape, if it's bottoming out before it snugs. – Mazura Mar 26 '16 at 23:11
  • This worked! I'll tape up everything and hopefully it'll withstand the pressure. Terrific pictures and explanation, thanks for ur help! – Lennart Mar 27 '16 at 12:44
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You should be using fittings that are applicable to the application, and should not be mixing and matching thread types. If you need to go from a fitting with tapered threads, to a fitting with straight threads. Then you should use an appropriate adapter.

I'm not sure why you're anti-PTFE tape. It's cheap, easy to use, and works well. PTFE tape is not specifically designed to seal threads, even though that's how it's commonly thought of. In fact, PTFE tape reduces the friction in the threaded joint. This allows you to get the joint tighter, which lets the fittings seat together properly. This is especially effective with tapered threads, though can also help seat straight thread fittings as long as it's not over applied. When working with straight threads, you'll find that paste dopes work better than tape dopes.

If you're looking to design a system that can be disassembled, and reassembled often. Then you're going to want to use fittings that don't rely on the threads to make the seal. The fittings may be held in place by threads, but the seal itself should be independent of the threads. If the seal is dependent on washers and/or O-rings, you'll want to be careful ow much you tighten it down. Crushing and/or deforming the washer/O-ring, can actually cause leaks.

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Sorry for my original answer Lennart. I was thinking the red thing was an upside down compressed air tank & this was all pneumatics, though I did see your plumbing reference initially.

That's a lot of fittings & looking at it a 4th time, you look fine on matched fittings. However they do look thread bottomed, meaning you're out of threads for anymore tightening.

That would be the reason for leaks & you really shouldn't need tape much of anywhere. The "plumbing secret" is rubber type stuff. You need a lot of Washers &/or O-rings to make this work, at just hand-tight, without a single drip.

You'll have to get a box of "Assorted Washers &/or O-rings" at the store since none seem to have come with any of the fittings. Measure the receiving cup for sizes you'll be after. Washers for wide cup shoulders (if any) & O-rings for very narrow cup shoulders.

I don't know what you're doing & of course I know you don't know what you're doing, but the brass item & the 1 or 2 fittings on either side don't seem necessary. I thought it was a ball valve, but I can't make out a handle anywhere.

  • Yes, but this isn't pneumatics but with water. I don't think the requirement will be as harsh as with high pressurized air. Would it be reasonable to tape it all up then? Is there something I can use between the parts, in the threads? – Lennart Feb 23 '16 at 16:28
  • Thank you, I corrected my answer. You should be able to mostly abandon the tape & replace it with possibly just O-rings. These will do a much better job & you'll be able to repeatedly take it apart & reassemble it as needed. – Iggy Feb 23 '16 at 19:14
  • Please read my original comment. If your straight threads do not have a grove for a O-ring puting one on it may still leak with a mix of thread types. – Ed Beal Feb 24 '16 at 14:50
  • Yeah, it's not a great picture & I credited & agreed with you perfectly in my first answer. But, looking at it a few more times I couldn't make out any separated connections that indicated a very short screw-on that a straight thread would have in trying to go on a taper. I'm interested to see if anything works after the wrenching he says he did, hopefully it turns out solid. – Iggy Feb 24 '16 at 14:58

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