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Flap Valves

Please call for pricing on 03302 230 275

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 Flexseal 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.

Flexseal offers 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.


  • High quality range manufactured in the UK, already supplying to the Environment Agency and Water Companies
  • Lighter weight than traditional cast iron flap valves, leading to easier installation and lower installation costs
  • Heavy duty HDPE will withstand being struck by rocks and other debris, present in marine and river environments, which would shatter lighter weight plastics
  • Waterproof qualities all the way through, not reliant on maintaining an added layer
  • Not at risk from theft as no inherent scrap value
  • Stainless steel hinges require minimum maintenance
  • All models up to DN400 can withstand a constant pressure of 6 mwc as standard
  • Technical support available from Flexseal
  • 25 year minimum life expectancy
  • Manufactured to DIN 19569-4
  • Our flap valves are supplied in accordance with ISO 9001:2008 requirements
For more information on Flap Valves please contact our sales office