How can illegal sewer connections cause basement flooding?
A surcharged sewer flows at a level greater than the “normal” level. If the home has sanitary fixtures or floor drains at an elevation below the surcharge level, basement flooding can occur. The sanitary sewers have been designed to transfer sanitary waste only. Extraneous storm water flow added to the normal sanitary flow can exceed the capacity of the sanitary sewer resulting in a situation where the sanitary sewer is “surcharged”. Basically, surcharging occurs when the amount of flow trying to get through a pipe exceeds the maximum capacity of the pipe thus building up pressure in the pipe. When pressure builds up it seeks to relieve itself through any means possible, one of which is by backing up private sanitary services and filling basements and crawlspaces. Reducing the extraneous flow will reduce the surcharging and sewer back-ups.
