Valves are generally fitted below ground on an outgoing pipe from a property usually within the last manhole chamber prior to the main sewer.The valve will shut under pressure should a main sewer surcharge and prevent flooding upstream through the connecting line. Anti-flood valve installations to: prevent backflow through drainage systems, sewer surcharging, back-up during heavy rain, property flooding, basement flooding, sewer flooding, back surge prevention, system isolation, flood defence and pump station failure. Prevention of flooding from rivers, brooks, culverts and streams. Made out of PE material. Produce in size from 50 to 200 mm