HamRad - thanks for the suggestion. I'll call him & see if he is willing to try it. I suppose the worst that could happen would be for only a partial opening, but he has a sewer hose for that. I know he won't try prying the valve open as suggested above because that means the unthinkable - exposure to the contents with the drain hose disconnected. I was hoping there was some trick that someone knew about that was simple and not risky. Like the time my black water tank was completely full and when I opened the valve just a trickle would come out. I knew I wasn't going to remove the drain hose and reach up there with a coat hangar or such. A true friend suggested we disconnect the drain hose from the park sewer outlet on the ground, raise it up about chest high, fill it about halfway with water and then lift the drain hose up and down to let the water push against the blockage at the valve. It worked. After a few sloshes up and down, a quick connect to the sewer drain and all came out. Apparently no such luck on this problem. Oh well, I'm just glad it's not MY problem. My son is young and more easily able to learn from this experience than I am.
