Airstream interstate 24 won’t drain black or grey tanks

[Leslie702]

Please help! I have an airstream interstate 24 and I can’t get the black or grey tank to empty. I have looked at all the posts here but my situation is a little different than what I could find. I can open the valves and I see them open under the van. When I tried to initially empty it I had to turn the screw on the end other mascerator pump back and forth to free it up. Usually this works for me. This time I got the screw to move and the screw spins when I turn on the pump. It spins really fast in smooth.. maybe too smooth. Even when the pump is running nothing comes out. Tried both black and grey multiple times. All I get is a few drips. I tried adding more tank cleaner and filling with more water and driving for a few days hoping to break up something in the event it was clogged but no luck and now I have a full toilet! Could I have turned the screw too hard essentially breaking the shaft from the pump propeller? Is that even possible? Any advice would be greatly appreciated ! Thanks