Peggy, let's explore that, please
I removed and checked the pump the "pump assembly." The two main things that I focused on were the "top valve gasket" and the "base valve gasket." These two gaskets are made in such a way that it would be almost impossible to instal them incorrectly. The way the holes are punched to match pegs that protrude from the base or matching the molded shape of the unit, I really feel that these are installed properly. Per your earlier suggestion, I checked and the tank was pumped to empty. This problem did not start until I changed out the parts from the "Service Kit" so I think that is a pretty strong indication that the problem lies in the changeover of parts from the service kit. But, following up on your latest idea that something else must be causing the backflow, when waste is pumped upstream into the line going towards the waste tank, what is there that would prevent backflow into the head? Wouldn't that be the joker valve? What else would prevent fluid from backing down the lines? BTW, the fluid that I see in the bowl is not terribly dirty, to be delicate, but, is slightly colored --- which would indicate to me that I am not getting backup from the tank, but from the fluid that has not quite made it to the tank.Anyway, that's my latest observations. Any additonal help would be appreciated.BTW, West Marine is replacing the defective "jocker valve" at no charge and sending it in 2nd day UPS. Cheers to them! Hisses to Jabsco for another cheap part that is taking way too much time to deal with.Thanks,Wynn FerrelS/V Tranquility