Black Tank Dump Valve

I use a end termination valve as well too BUT I am surprised nobody has mentioned that the valve will not close all the way is because toilet tissue got stuck in the knife valve and when you closed it and it jammed the tissue in the slot even more it has happened to me a few times (and many of us) take the underbelly off not a big deal just a few bolts on each side and in the middle underneath peel back the underbelly material and you will have full access to the valve take the valve off and clean the old tissue and other gunk in the valve and while you are at it smear plumbers grease all over both sides of the knife blade to make it pull in and out better and reinstall no big deal just time consuming