Flap valves are designed to operate under very low heads of water, in gravity flow applications, at ambient conditions between -65° and +85° C. The valve prevents backwater via a spring-loaded or weighted flap placed across the opening of a pipe, tube or duct.

In Tecence Engineering Flap Valves, the flap and back plate are manufactured in HDPE, with a stainless steel 316 hinge-pin, counterweight and attachments. Due to the specific gravity of the HDPE, a stainless steel counterweight is fitted to ensure closure when back-pressure is present; however very low heads of water are required to open the flap, as the design is such that the counterweight balances the flap correctly.

The Flap Valve incorporates a lip seal, to provide the seal between the flap and frame, and also a self-adhesive neoprene seal to install between the frame and wall, which is fitted to prevent leakage.

Foffers wall-mounted flap valves up to and including 1000mm in size and spigot-mounted flap valves up to and including 600mm. Flange-mounted, tidal flap valves and bespoke flap valves are available on request.