The membrane of the Stop Silent® SL13 backflow preventer is closed as standard when installed.
and is firmly anchored in the pipe using an expander clamp.
As soon as wastewater from the toilet, bathroom or other sources hits the closed membrane, pressure builds up, opening the sealing lip upwards and allowing the wastewater to drain away unhindered. As soon as the water flow stops, the sealing lip automatically closes again and closes the backflow flap.
In the event of a backflow from the sewer system, the sealing lip of the rubber membrane is pressed downwards against the pipe wall, closing the pipe force-fit. This effectively prevents backed-up wastewater from entering lower-lying rooms such as cellars.