Head

[Chris Burkard]

There are in-line valves from the toilet to the tank and from the tank to overboard discharge. They are one way valves called duck-bill valves. Flushing the toilet when the tank is full can over pressurize the tank and cause pressure to pulse back to the toilet inverting the one way valves in the wrong direction. This would then allow waste to travel from the tank (especially if it was full) to the toilet. If you have overfilled your holding tank, you will now have to replace the charcoal vent filter in addition to replacing the duck-bill valves. The charcoal filter is designed to filter fumes, not liquid. Once liquid enters the filter, it is ruined. If you don't replace it, your boat will begin to smell like a sewage treatment plant within a few days.

Good Luck!