What causes a sewer backup?

Sanitary sewer overflows can be caused by a number of factors. They usually involve sewer pipe blockages in either main sewer lines or service laterals (lines between buildings and the main line). Causes may include pipe breaks or cracks due to tree roots, system deterioration, insufficient system capacity due to residential or commercial growth, or construction mishaps. In home and office plumbing systems, the main cause is accumulation of grease, tree roots, hair, or solid materials, such as disposable diapers or sanitary napkins that are too large for wastewater pipes to handle. Such materials may cause major backups in City lines as well as in residents’ lateral lines.