Well, DS' nappies!! 
I thought you were meant to do a cold rinse, no detergent, then a normal wash at 40 or 60.
If I select pre-wash, that is part of a full wash and takes a couple of hours. If I select rinse, that is part of a full wash an added on at the end of the normal wash bit. There doesnt seem to be be a way to only do a rinse on my machine :-/ I have read the manual.
I've currently got a cold wash on with no detergent, to rinse, and when that's done (1.5hrs), will do a wash with detergent. Seems very uneconomical. I'm not a laundry whizz and need tips!!