I have had this exact problem. Im told that my main sewer line is blocked, or damaged and needs to be cleared. Of course, at this very moment, Im waiting for a rooting company to return and clear the line again as the problem has reoccured. If anyone knows anything else on this, Id love to know, too.: : Sewage is backflowing through my basement shower drain. Also, the basement toilet bubbles when the basement shower is running and/or when we run water upstairs. Any suggestions would be greatly appreciated.