During the last trip, the black tank flush stopped working. I removed the membrane enough to reach the hose and disconnected it. The hose connects to the flush fitting via a 90 dg barb adapter. After removing the adapter, there is a 4" X 1/2" screen tube with hundreds of small holes that sticks into the tank. I removed the screen and it was packed with lots of TP. I also found that TP had entered the 90dg adapter and the supply hose and had clogged the supply hose about 2-3" back up the hose. I flushed the hose, cleaned the screen and all works fine now. There are no moving parts. I thought about installing a Tornado flush, but that would require removing more of the membrane and drilling a new hole in the tank. I decided against it for now. Pretty easy job. I think the main problem is that the flush fitting is too low in the tank. Mine sits about 3" up from the bottom so is almost always "in the goo". It would be better to have it 2-3" from the top.