Many older commercial properties and factory units have internal drainage systems that discharge directly into public drains or local water courses, streams and rivers. In the advent of a flood these pipes and conduits provide one of the first lines of access for flood water to get into property and if unprotected can cause widespread flooding from manholes, gully’s and through ground level toilets.
Rising water in existing drains and water courses prevents gravity flow to empty existing systems and water flows uphill until manhole accesses and gully pots fill up to a point where surcharge water begins to discharge through the surface covers and low level toilet washroom facilities to create local area flooding.
Backflow into pipes and culverts can be prevented by installing non return valves or flap valves into drainage systems. These can be either surface mounted on outlet walls or internally installed inside manholes at any point in a drainage run. NRV’s and flap valves come in a variety of sizes from 50mm through to 1.8M diameters and larger if custom specified.
NRV’s and Flap valves allow water to flow normally under gravity when flows are low however as soon as water levels start to rise above invert the valves self-seal and stop water ingress into the system. Often used in conjunction with a flood alarm to provide early warning of potential flooding.