I'm currently using the thin wall PVC for the drain from the sink to
the floor drain. It's that thinner walled stuff you see iat Home
Depot that is used for P-traps and other sink drain stuff.

The ball valve I want to get is slip-slip and appears to be schedule
40 PVC. Is it OK to glue the schedule 40 PVC to the thinner walled
stuff that I'm currently using for the drain?

Thanks,
Clocker