I am still having a problem with waste backwashing into my Jabco toilet. I posted the problem several months ago and since then have replaced the whole toilet. It resolved the problem for a while but on it's back. I have flushed the system from the toilet to the tank, I have cleaned the vents, I have emptied the tank and still have the problem. I did not have this problem with the old toilet until I had the discharge hose replaced last year. I replaced the old black hose with a new white hose that is not suppose to smell. I did notice that there is a joint it the hose very close to the lowest level of the run from the toilet to the holding tank. There was no joint in the old hose. I'm beginning to suspect that waste gets trapped in the area where the joint is over time and that is the reason it works for a while and then starts backwashing. I can't think of any other answer. Any ideas?