I have an Itasca 36F that has 2 bath rooms. Love the floor plan but I have a problem. The small mid coach bath room has a terrible odor as does the compartment below where the black tank pump is locat...
I had a similar situation. I used some bleach and calgon water softener. Filled it up to 3/4 full. When I arrived to the campground I dumped the tank leaving the fresh water flush going for an hr. Just remember to leave the dump valve open. Besides solving the odor problem my sensors started working again. Keep those tanks clean. Good luck.