PPS 15 Planning and Flood Risk (Revised)·Page 78
Non Return Valves and Covers
Drainage and sewage pipes should be fitted with one-way flaps, and manhole covers and air vents should be sealed or fitted with water-resistant covers to prevent backflow during flooding.
Flaps can be fitted to the end and junctions of drainage and sewage pipes to stop any water flowing back into the building. Manhole covers can also be sealed by being bolted down and air vents can be fitted with specialised water resistant covers.
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