What can I do to eliminate blockage in the main drain line? I have a two story home with 2 bathrooms upstairs and a half bath downstairs. A few days ago, I flushed the downstairs bathroom before I went to bed with no solids, and in the morning,we witnessed an inch of water on the floor, but very low level of water in the toilet. It appeared that the tank lever did not close and the water kept running into the toilet bowl. But how did the drain line get clogged up, and then somehow opened before we came down? Sometimes, we experience clog-up with just shower running or washer draining. Could there be a fault in the sewer line connecting the houses on the street? The street is slightly sloped.