Thank you very much for sharing your experience Oren,
Richard, Mamba, Joe, Jim and Franz. It's raining here today,
so I am not doing more than a little measuring, cutting, and
gluing. I will try the teflon piping dope.

I have been learning the hard way that the key to a good
thread fit (with PVC) is not overtightening, so the
re-emphasis on this by several of you helps.

I will report back after the job. It's a little tricky
because I have to glue other joints before I can apply the
operating pressure to the two adapter-valve joints under
discussion. And as you all know, once glued... I may put in
unions to help ease the pain of a mess-up at the valve(s),
due to yours truly not being experienced enough in plumbing.