Heavy rainfall can overwhelm home sewer systems and sump pumps, causing sewer backups that flood basements. Old sewer systems, tree roots, and blocked lines can all contribute to backups. While the causes may be out of homeowners' control, insurance can provide peace of mind for flood damage. Homeowners are responsible for sewer lines from their home to the main line, so they should contact local authorities about insuring these lines, though insurance does not cover line maintenance or repairs.