RV Repair: dump valve, slide valve, holding tank

Question
I have a dump valve for the toilet that will not release.  What is the best way to go about getting it to release so I can dump the holding tank?

Answer
If you are talking about the large slide valve that dumps the black water tank, it's probably just stuck and needs a little more yanking to get it loose.  If you can get to one side of it, squirt a little oil around the rubber lip and see if that does not help.