I had a similar problem with the rear toilet in my Winnebago Tour. The drain problem only occured after I had the toilet moved forward as the lid wouldn't stay in the upright position (too close to the wall) Anyway, I called the manufacturer and they told me to check the black 1 1/2 inch rubber pipe on the back of the toilet. If it's too low, the toilet will drain. I found that the hose slips into a rubber coupling near the floor and all I had to do was to wedge the black pipe so it was higher that it was. I took a piece of 3/4" wood and made a "U" shaped wedge that slipped under the coupling hose, resting on the floor which in turn raised the black pipe 3/4 on an inch. That stopped the leak down. If you need more info. send me a message and I may be able to take a photo but once you look at the black pipe especially where it goes through the floor, you'll see how to make a wedge as I did.
[SIGPIC][/SIGPIC]2016 Newmar Dutch Star 4369
Newmar Owners Club
USAF 1966-1969,- Law Enforcement 1969 - 2003, Retired since March 2003