Closing off the sewage system

In the event of a flood, the backing up of water in the sewage system means that waste water can inundate the surface or enter surface water, with environmental damage as a result.

This risk can be reduced by fitting check valves that shut off the sewage system when there is back-pressure as a result of a flood. You can also install shut-off valves. This stops water entering a dryproof building from the ground level through the sewage system.

• Applicable to land and buildings;
• Spatial adaptation and crisis management;
• Permanent or temporary measure;
• Limited investment;
• Prevents economic and environmental damage;
• Applicable at all flood depths.

Shut-off valves are located in sewage systems and they are usually open to make the water flow into the sewage system from a building or outside locations. They close automatically as soon as a pressure sensor detects a change in the flow direction. This stops water entering the building from the sewage system, or ensures that dirty water from the sewer system does not come into contact with surface water and contaminate it.

A check valve is a permanent system that closes when there is more pressure from outside than inside and you can use it for the same purpose.

There are some areas requiring attention.

• It is important to be able to operate valves manually, for example when there is a malfunction.
• The weather can often be windy and rainy when water levels are high. Rainwater must not enter the building if the shut-off valves are closed. So there should be overflow options;
• To ensure that processes can be maintained for a period of time, some buffer capacity in the drainage system from the property is desirable.