If your sewer line is backing up repeatedly, and if the usual procedure of having it cleaned out with a sewer tape or power auger isn't solving the problem, it's an indication that your sewer line may need to be replaced. The usual cause of this is tree roots, which push their way into the joints and cracks of the pipe. If the damaged line is isolated to one section of pipe, a partial replacement may take care of the problem. If the whole stretch of line between your house and sewer main or septic tank needs to be replaced, you'll have to contact plumbing professionals. It's a major job that involves the opening up of a trench to lay the new line. Consult a plumber in your area for more information.