[Shane826]

There is not a black tank underneath. The toilet is the black tank. But if the toilet is full and you need just a little bit more capacity to make it one last overnight, here’s a little trick… Make sure the outside dump valve is CLOSED. Double check that it’s closed, otherwise you’ll be in for a rude surprise later. Now pull the inside valve underneath the toilet. The stuff in the toilet will drop down into the plumbing underneath, giving you about an additional gallon of capacity. Now when you get to the dump station just hook up the hose pull that outside valve to dump like normal.