dm2776, a few questions. Do you have the ceramic toilet? Does the toilet hold water or does it loose water through the ball seal? Can you determine if it's only leaking when you flush? Have you just started using the camper and has it leaked since day 1. You could have a bad seal at the floor flange or a bad seal at the ball valve. The flange seal on the floor is easiest to check and replace. It's very similar to a home toilet except the seal is rubber and needs to be in just the right position.