Water leak from brass and copper threads.


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Old 05-02-21, 09:16 AM
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Water leak from brass and copper threads.

Hello everyone and thanks in advance for any help. I am installing a new shower valve in a shower makeover. The new valve has female threaded brass connections for the hot, cold, tub spout and shower head. The pipes are 1/2 copper. I bought threaded male adaptors made of copper with a 1/2 inch copper union just in case the threads leaked. I put 3-4 wraps of teflon tape and tightened the adaptor into the brass. It leaked, so took it off and added one more wrap of tape with rectorseal T plus 2 pipe dope. It slower but still has one drop about every 2 hours or so. I have tightened the fitting about as tight as I feel comfortable with, I don't want to strip the brass threads. Last night I placed a bead of Silicone on the outside of the threads. Is there anything else I can use or should I just leave it alone and let it seal itself? I would love to solder it as my solder skills are good, but I don't think that would be a good idea.
 
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Old 05-02-21, 10:21 AM
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hi homownr -
took it off and added one more wrap of tape with rectorseal T plus 2 pipe dope.
You mean that this time you used 5 wraps? I guess so – because you need to start from scratch to re-wrap. I use Rectorseal # 5 and I think I use more than 3-4 wraps (maybe 8-9?). I know a lot of folks say don’t use that many wraps – but I do.

I then cover the tape with a generous amount of RectorSeal 5 and then really use some muscle to tighten things up.

I have a feeling you aren’t tightening up enough. I don’t think you can harm the threads. But see what the experts say. My understanding is that usually the problem is not tightening enough.

(I think Rectorseal T 2 would be OK)

 
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Old 05-02-21, 10:36 AM
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I've done many copper fittings, threaded and soldered. Threaded pipe fittings seal via interference. Which means the threads are tapered to force a seal. TFE tape or paste is used to lubricated the threads to make it easer and to some extent help seal. TFE tape is not meant as the sole sealant for pipe fittings. Zoesdad is correct, you are not tightening enough. But I disagree with him on the over use of liquid or TFE sealants. Those should not be necessary. If you're unable to get a leak proof connection then try soldering or perhaps SharkBite's.
 
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Old 05-02-21, 11:40 AM
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Yes each time I took it apart I cleaned the threads and started from scratch. In your opinion which would strip first the male copper adaptor or the female brass threads on the shower valve? If the copper striped I would just sweat on a new adaptor. If the brass striped that would mean another valve.
 
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Old 05-02-21, 11:55 AM
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The copper should be softer.
 
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Old 05-02-21, 01:22 PM
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Stripping threads on a 1/2" NPT fitting has probably never occurred EVER, so that is not even an issue.

Adding silicone on the outside of a fitting to stop a leak is also a completely ineffective thing to do.

When you tighten a fitting, you need 2 wrenches, and you tighten it until it is snug. Not as tight as humanly possible... but tight. If you are using enough PFTE paste and tightening it enough, it should not leak. If it does leak, its not tight enough.

If you are using only 1 wrench, that is the problem.
 
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Old 05-03-21, 09:33 AM
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I want to say thank you to all that replied. I was using 2 wrenches on the fittings, but was afraid of stripping the brass threads on the shower valve. After reading the replies I backed off on the union and tightened the male adaptor into the shower valve some more and low and behold the leak stopped and the threads did not strip. Thank you again.
 
 

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