Originally Posted by fbconsults
When I try to introduce water into the black water holding tank through the black water flush system, it seems to be plugged somewhere. My first thought was the anti backflush valve where the external water hose attaches was stuck, but when I depressed the valve, water squirted out. I assume this was from the backpressure in the line. I wonder if threre is another anti backflush valve somewhere. It doesn't seem like just "stuff" where the water sprays into the tank could create this problem.
This is what I think because I had a similiar problem just a few months ago.
I was washing out my black water tank and suddenly no flow. I could not hear any water flsuhing in the tank.
I checked my back flow preventor inthe closet but it was ok and I did what you did and got wet.
The problem was the sprayer that enters the black water tank got paper in it from the tank. Not sure how but I had to remove the cover of my hot water tank cover to get to it. It was located in the upper right hand area. You should easyily see it. Blue hose and a 90 degree fitting
It screwed into the tank and was sealed with silicone. I unscrewed it and found paper lodged in it. I took a small screw driver and cleaned it out and reinstalled. Everything worked great but I think some how the black water tank pushes paper back into the valve.
Anyway hope this helps you