toilet back flow to tub when plugged? HELP - am confused! I thought I had a plugged toilet - walked into the room and the water was at the top of the rim and slowly running over the edge and I had not even used it for 20+ hours. I used a plunger and flushed only to have water everywhere and now the water is coming up in the tub drain and it wont drain out. It is a second floor bath in a 30 yr old home. How does the toilet connect to the tub to fill it with water through the drain?