In article , IMM
writes

"fred" wrote in message ...
I agree, with all of Andy's comments, but would add that my own rule is
never to use a fitting that is mechanically weaker than either/any of the
pipes to be joined, so if I am making plastic/plastic I use plastic,
copper/plastic I prefer to use compression and copper/copper I would never
use plastic. All to do with the risk of stressing/damaging the fitting
when
pipes inevitably get moved about during fitting and in the months/years
down the line.

Can you elaborate please.
I was suggesting this as a protection against abuse/accident rather other
kinds of movement.
--
fred