a device that prevents sewage in an overloaded main sewer line from backing up into your basement

a fixture installed into a sewer line, and sometimes into a drain line, in the basement of your building to prevent sewer backflows

a fixture put on a sewer line, and sometimes a drain line

a plumbing device designed to automatically shut and prevent sewage from entering internal systems in the event of public sewer flooding or obstruction

a plumbing fixture that acts as a one-way stopper

Sewer line valve that prevents sewage from flowing back into the house

A valve in a sewer line that prevents sewage from flowing back into a house.