The Stop Silent Light duct backwater flap is designed for a use in industrial and private waste water. Lasso Technik AG check valves can be used with a back pressure of up to 0.5 bar. Quick and easy installation in the drain pipe is ensured by a friction clamp inside the valve. Our check valves also have a nose flap function and prevent all small animals from entering the sewer system. All our products are also equipped with an airtight odour check valve so that no duct gas can escape from the cellar.