I don't disagree with what has been mentioned as far as the check valve preventing the fresh water becoming contaminated, however, in the Montana 3400RL the water line is installed in the wall of the bathroom. This means that the tubing is elevated approximately 4+ feet above the black waste tank then drops back down to the waste tank where it is installed in the top of the tank. The only way there would possibly be cross contamination would be if the tank were totally full, the hose was hooked up and there is no water pressure at the spigot and even then the waste would be backed up into the toilet since where the check valve is located is above the level of the toilet. Most people do not leave the flush hose hooked up. I do agree that there could be contamination, but not likely. Just my opinion.
