Our bus restrooms, even the ones that flush, are much simpler than Amtrak’s or airlines. They do not employ a vacuum system that is prone to clogging. Instead, they rely on gravity.
As for odor control, the powerful chemical, added to the holding tank, usually does a pretty good job. But in extremely heavy use, or if the tank is not dumped and flushed at the proper period, odor can become a problem.
In the past, if far from a servicing location we would add some additional chemical, but for some it became an irritant.
We did discover another remedy that would solve the problem temporarily, much better, and at low cost…
Simply pouring in a capful of Downy fabric softener worked miraculously, stopping the odor, and didn’t seem to irritate anyone.
All our buses soon carried a bottle…