Pat,
We have owned 3 Trailmanors since 1992, and I have never had any odor problems with the recirculating toilet. At Walmart, I buy Thetford liquid Campa Chem Natural formaldehyde free holding tank deodorant. It comes in a box(6 bottles). I use one bottle per charge. To save on holding space, I do not bring the water level up to the line where it says that it is charged.
Also, I bought at Camping world Potty Toddy Tabs. I just add one or 2 tablets in along with the blue Thetford Campa Chem. Even this last Summer when it was very hot, we never got a smell using the combination. We have used it for 4 days (3 adults) before I had to dump the toilet. When we stay for over 4 days at a campground, I always get full hookups. If we are there for less time, I just use the dump station on the way out.
I have recommended this comination to friends, and they too have never had any problems with their recirculating toilet no matter the temperature or what went in the toilet.
When we owned our 1988 Coleman Plantation, it had the built in Thetford toilet. It was not a recirculating type, but the directions way back then said to use this combination for best results. I tried it, and it sure did work well.
Just give it a try, and I am sure you will be happy.
Bob Strong