Toilet in Mid Bath November 21, 2015, 01:34:12 pm Yahoo Message Number: 157092Hi Melinda. I think the seal that Ken mentioned should have been nine inches in circumference, not diameter, if they seal the "white flush dome". That dome is a valve, operated to open the entrance into the black plumbing tube(s) leading to the blackwater holding tank. My TK has the toilet lead directly into the tank, but it seems that most motorhomes and trailers have the tank some distance away. The black rubber seal at the base of the toilet against the floor is about 9 inches in diameter. If the opening at the base of the toilet bowl isn't white plastic, then maybe the return spring didn't return the valve to closed. I haven't looked at this part since mine is still working. Hope this helped. RonB in San Diego.