DO NOT use the CPVC "female" adapters that have the threads cut into
the plastic. I don't think they are allowed by code anyway. I've tried
them in the past and when the metal "male" adapter is threaded into
the CPVC "female" adapter, it cracks the female adapter. Happens
almost every time, no matter how careful you try to be.

You must be doing something wrong - that's *never* happened to me, and
they never leak, either.

I "have" made many successful connections with female threaded CPVC
adapters, but I've also had enough failures that I know not to use them.

The PROPER way to make these transitions is with a TRANSITION UNION. They
are strong, ensure leak free connections, and accomodate the different
thermal expansion rates of the dissimilar materials.

Anthony