From the Manufacturer
This simple devices offers effective protection against the backflow of sewage and stormwater into homes and businesses. Under normal operation, the lightweight flapper opens and lets in waste water to exit to sewer line. All the way through a backflow,the flapper seals closed, stopping the drift from reaching interior drains entering the living space. Backwater valves (BWV)are beneficial on all branch lines serving low level appliances, leaving the principle line open to discharge and vent. Any drain openings at the back of the BWV are safe from backflows. A BWV may also be installed at the main line before it enters a building.
Protection against the backflow of sewage and storm water
Compact, lightweight and easy to put in
All Canplas Backwater valves are socket x socket with all sockets being DWV
Acme threads provide positive traction and extra strength
Neoprene O-ring effectively seals valve lid