Thanks for all the responses. Very helpful and good ideas. I have the anti-siphon valve under the sink. Should it be open (easily twists to left or right) or should it be tight? I will mess with it to see if the odor is reduced. And I will not run the vent fan unless not using it makes it worse. The odor is confined to the bathroom and on the outside where the flush values are located. There are no drips and my toilet bowl holds water. I also let water run into the tank to be the fecal matter is covered by water. This is my first motor coach and don't want it to be my last. My wife is ready to bail. Thanks again and any further help is appreciated.
Rodger
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