shut off valve leak


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Old 03-23-11, 07:24 PM
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shut off valve leak

I developed a leak from a shut off valve. I have a pvc threaded fitting and a threaded metal valve. No others in the house leak but this one. I have retaped and retaped and retaped but nothing works. I even bought a new valve. I then found a fitting that transitions from the pvc to metal threads and the valve screws onto metal threads. Now I have a worse leak than before. More tape, less tape - it doesn't matter! Any suggestions?
 
  #2  
Old 03-23-11, 07:30 PM
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The plastic threads might have lost thier taper. You can try to wrap the tape thin at the start of the threads and build it up thicker as you move back. Puting your own taper on it. Add some teflon paste after you tape also.

If you dont what to be bothered trying anymore, cut the threaded part off the pipes and get a shark bite valve. Push-push, done...

Mike NJ
 
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Old 03-23-11, 09:00 PM
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My experience with plastic threads and Teflon tape is that it ALWAYS leaks. Use a semi-liquid thread sealing compound (such as Teflon paste) compatible with plastic and it will seal.
 
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Old 03-24-11, 09:56 AM
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hi guys Ė

charger I was looking into the same kind of adapter that I think you are talking about. I have pictures of some but I canít find where I got them. Iím sure they are PVC. Is the adapter you are talking about something like this? This one is cpvc but itís the same idea.

Adapter, 3/4 In, Slip x MPT, CPVC, Copper - PVC and CPVC Pipe Fittings - Fittings - Plumbing : Grainger Industrial Supply

If so then it seems to me that you have plastic out of the equation. If I understand you have a brand new female threaded valve and a new adapter with male metal threads like the above. And I think you are saying you are leaking at the threaded side not the pvc glued side. If you are varying the amount of teflon tape you are using and it still leaks- I donít see how you could be doing anything wrong?

Wonder if itís the threads on the adapter itself? I thought I heard that there are problems with those types of adapters. But I donít remember where I heard that or what I heard about them (real helpful huh).

Wonder if the experience guys here have any opinion on the above type of adapter? (Hope I understood what you are saying and I am not way off on a tangent).
 

Last edited by zoesdad; 03-24-11 at 10:35 AM.
  #5  
Old 03-24-11, 03:13 PM
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I've also found out through experience that brass-to-brass threaded fitting will often (but not always) leak when using just Teflon tape. The Teflon paste is also the cure in this instance.

Quite honestly, I find that Teflon tape alone is problematic when joining threaded fittings and when I use it (less and less as time goes by) I always use a Teflon paste with the tape. In my opinion the only positive quality of Teflon tape is that it is clean and easy to use.
 
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Old 03-24-11, 03:41 PM
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Yes and the funny this is, on the plumber test in NJ they ask you if teflon paste/tape is a lubricant or a sealant??



If you said sealant you got the anwer wrong.

Its a lubricant that allows you to turn the threaded fitting into the taper further to prevent leaks.

Just incase anyone was wondering.

Mike NJ
 
  #7  
Old 03-24-11, 04:21 PM
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Teflon tape is a thread sealant. If the NJ test says that it is a thread lubricant that is only partially correct. It's teflon it has lubricating properties. But is they say that teflon is not a thread sealant they are wrong.

This comes up every year or so. Most plumbers have been taught that the tape is a lubricant - it is - but it was marketed by Dupont as a thread sealant. You can also find articles on the internet that state that the tape works because it allows the joint to be made up tighter and the threads deform to make the seal. That is also not true. The tape seals by filling thread anamolies not by deforming them.

I used teflon tape in high pressure system testing for years as the only seal in mechanical joints up to 4500#. The last thing we wanted to do was deform threads.
 
 

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