How can sump pumps cause basement flooding?
Overloading the sewer system from sump pump discharges can lead to sewer backups and overflows. The sewer system capacity is for wastewater flows only, and the addition of outside water sources can cause the sewer system to backup and/or overflow. When the sanitary sewers are overloaded, the water level in the manholes and sewers rise. When it rises above the level of your basement floor, the sewers can backup into your basement. See the drawing of Sump Pump Incorrectly Discharging to Sanitary Sewer”.
