MM49 wrote:
Some campers have block in them from inital manufacturing. The hole saw blank from the pipe cut in might not have been removed during construction. slow drainage is the first sympton.
MM49
That was my next thought. Either one of the cutouts dropped into the tank =or= the inlet pipe may have come off and is too close to the bottom and not letting things drain properly. I think the plumber, with a camera, might be in order so the OP can =see= what's going on. I've had one poop pile in my rig when I was trying to save water on a boondock, but decided that it wasn't worth it the next year! :-)
Lyle