I have a Wilcox-Crittendon (Sp) head with a holding tank. There is always some water left in the bottom of the toilet bowel after I flush it. I pump and pump, and it does not come out. I got a rebuild kit and overhauled the pump, but no change other than greater water flow. Is this ok, or is it an indicator of some other problem? We sometimes have an odor problem in the summer, but I suspect it is caused by guests not knowing to use enough water in the wet mode and leaving some sewage in the bowel.