|  Flap Valves Flap valves prevent the back flow of water from the receiving watercourse into the drainage system. Where any pipeline is at risk of being submerged by the flows in the watercourse or where the drainage system discharges to a tidal reach, then a flap valve may be installed. The designer should assess the possible adverse effects that may arise due to the use of a flap valve. The effects of sea water and tides buffeting the Flap Valve in coastal situations can cause maintenance issues, these can be overcome through the use of a "Tideflex Check Valve" which has no mechanical parts and therefore will not be affected. Where the Flap Valve is required to be fixed to the Headwall, Stainless Steel Sockets are cast in during manufacture. The Stainless Steel Sockets are secured to the reinforcement cage. The number and size of the sockets obviously correspond to the required Flap Valve, so if you know that a Flap Valve is required and you know which type is going to be used please mention it when ordering, this is especially important when a "Tideflex Check Valve" is being used as a considerable number of fixings are required. Where the outlet may be accessible to members of the public, the HDPE Flap Valves rather than cast or ductile iron may be less susceptible to vandalism. Ham Baker Ductile Iron Flap Valves 80 - 900mm Ham Baker Grey Iron Flap Valves 1000 - 2000mm Tideflex Check Valves 100 - 1500mm
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