"gonjah" wrote in message
...

Is there anything like WD40 for plastic? Something I can spray it and let
it soak for a while before I try to loosen the couplings?

WD40 is a solvent i.e. damages some types of plastic.

Pool piping in this part of the world:
1. is dissassembled every winter
2. with a (rubber) strap wrench if needed,
3. and reconnected every spring,
4. using Teflon tape to seal leak-free (six turns on
the threads of plastic screw fittings, and three more
on the butt, says local expert Sam who is always right.)

--
Don Phillipson
Carlsbad Springs
(Ottawa, Canada)