Elle wrote:
I am re-plumbing part of my pool filter system. Previously,
a 3/4-inch metal valve was threaded to 3/4-inch PVC piping.
The PVC piping had a PVC male adapter, which fit into the
female threads of the metal valve. I am replacing the male
adapter but find it is a very tight fit. A lot of torque
would be necessary to get it into the previous depth.

I find that PVC pipe, mostly from China now, varies in dia slightly,
so just screw it in until you feel it's tight. Water test for leaks &
tighten more as needed. Over tighten stresses the plastic!!

Tom J