Last year, when my holding tank cracked, I took the opportunity to replaced all of the hoses, much of it with hard pipe, put a new piston on the pump, changed the vacuum switch and rebuilt the valve/ball assembly...basically went through the whole system.

Now, I've got an odor, quite rank, that seem to be coming from the toilette when it's flushed. This in turn gets picked up by the air handle and distributed, with force, into my daughter's stateroom, and the galley.....yuck.

The only part I had not replaced was the base seal, so today I removed the toilette to replace the seal, which while ready to be replaced, showed no signs of leakage.

I was going to pull the base, but it's pretty well bedded. The area under base is inaccessible, but looking at the diagram of the system, there doesn't appear to be anything that can leak under there, without losing vacuum, which it doesn't. There's also nothing in the bilge that I can find.

I checked the vent hose, and the filter, which while old, can be blown through so I don't think it's a pressure build up at the tank.

So where can this puff of ill wind be coming from? Any ideas?