What is the most common cause of sewer backup?

There is no single cause to assume for every home or sewer system. Blockages from grease, wipes and other discarded materials are common; New York City identifies them as its most common cause. Roots entering damaged pipes, broken lines and overloaded sewers during heavy rain can also contribute. A recurring backup needs an assessment of the private lateral and, where relevant, the public main. Ask what evidence supports the diagnosis and whether clearing the line is enough or a repair is needed. Keep grease and wipes out of drains, including wipes labeled flushable.