One hint - there are two different sizes of pipe and fittings which appear the same size. On type is for gluing and the other is push fit. It is possible to mount the too-small type fitting in a lathe and bore out about 1.5mm so it fits the other kind of pipe - satisfying, yes, but not a good use of time.
And I've done the pouring the dirty water into the sink I've just disconnected as well - just after thinking "how can anyone be ao stupid as to so that"