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Flap Valves

A Flap valve is a type of non-return valve that prevents
liquid from returning back up a discharge pipe or a culvert.

Installation of stainless steel flap valves
A flow of liquid arriving from the upstream end of the system, will hit the back face of the flap valve door and push it off its’ seating face away from the frame – this allows the flow of liquid to continue.
Once the flow of liquid has ceased, the door will swing back and rest against the sealing face on the frame, once again closing the orifice.  Any liquid building up against the front face of the door or flap will serve to push the door or flap further against the sealing face on the frame ensuring a water tight seal – at this point no liquid can flow back through the orifice, thus preventing “back-flow”. Flap valves can be used in many applications and locations, including:
Flood Control
Sewer flooding prevention
Back-flow prevention
Culvert Isolation
River Outfalls
Tidal Outfalls

Flap valves are typically circular, square or rectangular
in shape dependent upon the application and consist of a frame (fixed to a
surface or pipe flange), a door (or flap) and a hinge and pin arrangement
from which the door (or flap) hangs.

Fish Friendly Flap Valve
Flap valves come in all shapes and sizes and can be made bespoke to specific project requirements, including but not limited to:
Fish/Eel Friendly applications
Pumped flow or gravity flow
Reinforced doors/flaps for larger scale openings
Reveal fix applications for when surface mounting is not feasible
Winching arrangements can be added to allow for manually opening the flap valves for ongoing maintenance purposes

Flap valves from IBS are available in the following
materials :

Stainless steel 304 or 316L
Duplex or super duplex
Flap Valves
Single Flap Valve
Generally, flap valves are fixed to concrete headwalls and sit over the outfall orifice, but they can also be installed on the end of an outfall pipe via a flanged connection or alternatively with the reveal of an opening itself if required. 
Flap valves normally protect sewage and surface water outfalls from back-flow due to flood and/or tidal applications. Flap valves can also offer odour protection by ensuring the outfalls are always closed when not in use.
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