Well...two things...
First, while coming down the chatter-bump filled mountain dirt road...unbeknownst to me, the black tank dump valve bounced opened just enough to fill that little chamber between the black gate valve and the sewer cap where you attach the dump hose.
I'll leave that to your imagination what that meant to me when I took the end cap off wearing shorts and sandals!
I bought that Valterra valve the very next day...
Plus, with this valve you can now use your gray water to back flush into the black tank to help loosen anything that may be stuck to the bottom of the tank!
I just did this yesterday and it is unbelievable how much this gets out...even with the built-in tank flush system my Prowler 5'ver has!