I have a 98 Classic Limited 34', and something appears to be hindering the operation of my black water dump valve. It doesnt seem to close all the way, is difficult to move, and it is difficult to secure the dump valve handle retaining clips. When I remove the bayonette connection cap, the drain pipe is full of blackwater debris. I have used lubricant, and worked the valve repeatedly, and had limited success, but within a week or so, the valve seems to still let waste by, only to be stopped by the "cap". Can anyone give me hints on an agent that will dissolve whatever is keeping this valve from getting hung up, or am I looking at a valve replacement?