pvc/cpvc joints

Reference pvc/cpvc threaded joints: do you need to add anything to the threads when making a connection? If so, teflon tape or joint compound? Is there any problem with transitioning from copper to pvc using a male copper fitting and a female pvc fitting? (I'm thinking possible expansion differences.) A salesperson recommended joints be hand tight only - is that enough? Red
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First, NEVER thread a male metal fitting into a female plastic fitting. The plastic fitting will crack or split everytime. I don't think female plastic fittings are even allowed by code, even though they are still sold in stores.
The best way to transition between copper and PVC is to use a dedicated transition fitting. I have seen two different types for CPVC. One is a molded threaded brass fitting with a CPVC fitting molded on the opposite end. The other (and the one I prefer) has a brass fitting on one end, a CPVC fitting on the other end, and a neoprene gasket between the two that is tightened down with a large nut (kind of like a union fitting).
If you have no other option, you could use a FEMALE copper fitting, and a MALE PVC fitting. I always apply a few wraps of teflon tape, and go a bit tighter than hand tight. The correct amount of torque to apply is kind of hard to describe, but you learn after a few leaky joints just what is needed. :)
Anthony
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Been to Lowes & HD and neither one has copper-to-PVC transitions of any type. Lowes department manager said they don't even make one. Found unions & transitions for copper-to-CPVC, but zip for PVC. Can't figure out why unless the schedule 40 fittings are much stronger than CPVC and don't require a special connector. Lacking any additional input, your "no other option" may have to apply.
Red
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wrote:

Been to Lowes & HD and neither one has copper-to-PVC transitions of any type. Lowes department manager said they don't even make one. Found unions & transitions for copper-to-CPVC, but zip for PVC. Can't figure out why unless the schedule 40 fittings are much stronger than CPVC and don't require a special connector. Lacking any additional input, your "no other option" may have to apply.
PVC male threads into copper or galvanized work fine in most cases. I have had OK success with metal into PVC female threads also, but I wouldn't do it in a behind-wall installation.
I think that CPVC might be more of a problem because hot water softens it.
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Red,

Since regular PVC is only meant for cold water, it probably doesn't expand as much as CPVC with hot water in it. So there's probably less need to compensate for the different thermal expansion rates of plastic and metal.
Use a male PVC and thread it into your female metal fitting. It'll work fine.
Anthony
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using a union will allow proper future tightening at future time of drips.
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