If a blockage occurs in the sanitary sewer system, sewage will rise through a manhole and overflow to the surrounding area. However, if your house plumbing is below the level of the overflowing manhole, the sewage can backup through your house side sewer lateral and enter your home through your plumbing drains. Backflow prevention devices are designed to prevent sewage from entering your home and are mandated by building code as well as District ordinance. When the need for a backflow prevention device is overlooked or ignored, the consequences can be devastating.
Please call the District if you need help locating your backflow prevention device. 415/435-1501