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I am replacing a 30+ year old shower valve as part of a master bath remodel. The existing shower valve has 1/2" NPT female ports (qty 4), with one port capped. The new valve has 1/2" NPT male connections (qty 3). I have these fittings in my possession:

1/2 CPVC female to 1/2" NPT female fitting

I'm just wondering if these are acceptable for this application.

A local big box store also (supposedly) has these fittings available: enter image description here

which do not have the nut and gasket. Are they both allowed? Is one better than the other?

I'm in Gwinnett County Georgia, USA.

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    You should not use a gasket for any joints which are inside a wall. NPT threads are tapered and are tightened with a "permanent" sealing of pipe dope or Teflon tape. A gasket will eventually dry up, shrink, or deform and leak. AFIK compression fittings are also allowed inside a wall as are various other new joining systems. Some local codes may prohibit certain joining systems which are allowed in other jurisdictions. Ask your local plumbing inspector. – Jim Stewart Jun 14 '17 at 14:38
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From what I can gather, both fittings are acceptable. I ended up getting the second style, and after installation, there was a very small leak at the NPT thread. I could not tighten it, since the CPVC does not rotate relative to the copper. So, I had to cut the line tighten the fitting and then install a CPVC coupling. Not a big deal, but had I installed the first type of fitting, I could have loosened the nut, tightened up the NPT joint and then tightened the nut. Which I suspect is exactly the problem these fittings are meant to address.

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