Have you ever had a pumper truck empty the tanks? We had a truck empty the tanks in our 2001 Adventurer at the Winnebago GNR one year. Since we had it pumped during the week we decided to skip emptying it at the local park before heading home. When we got home we had a mess running out of the wheel wells.
As it turned out the suction from the trucks pump collapsed the top of the black water tank. The pipe from the toilet had disconnected from the tank so there was a 3" opening on the top of the tank. 300 miles of rough road caused some of the contents to spill out the hole and run down the frame.
I had to remove the exterior rear fender panels and the sheet metal panels behind them to gain access to the tank. When I got there I found the black tank had actually shifted off it's mounting blocks. I was able to reposition and secure the tank, but had to take it to the Winnebago Service Department in Forest City to have them replace and reseal the PVC pipe that went from the toilet to the tank.
It was a messy experience that was thankfully resolved by the excellent technicians at the factory.
Hikerdogs
2013 Winnebago Adventurer