Non Return and Flap Valves
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Data Sheet |
Non Return Valves
Non return valves or backwater valves are used within sewerage and drainage systems to eliminate the risk of flood damage by the backflow of sewage into properties through low level entries such as low level drain gullies, toilets and washing machine outlets. The Environment Agency in their publication on damage limitation for properties at risk from flooding and the Government guidance note “Preparing for Floods” both recommend the installation of non-return valves (anti-flooding devices) on all drains and sewers.
The Building Regulations 2000, Approved Document H, recommends the installation of double flap non-return valves on drains from basements in low risk areas and on all drains in areas with a high risk of flooding or sewer surcharge.
Flap Valves
The principle applications for flap valves are for surface water drainage associated with river, estuary and sea water outfalls to prevent backflow into the sewer and for final effluent outfalls from wastewater treatment works to prevent flood damage within the works.