Wastewater from a rainwater harvesting system
In accordance with DIN 1989, the overflow from rainwater storage tanks must be connected to the sewerage system in a backflow-free manner. A distinction must be made between:
- When connected to a rainwater sewer, protection can be provided by backwater valves of type 0, 1 or 3 in accordance with DIN EN 13564-1
- When connected to a combined sewer, drainage must be provided via a sewage lifting station in accordance with DIN EN 12050-1
With regard to dimensioning, a design rainfall intensity r(5,100) must be applied.
Wastewater from small-scale treatment plants
Small-scale sewage treatment plants must also be installed in such a way as to prevent backflow. If there is insufficient head between the operating water level and the backwater level, there is a risk of disruption to the treatment plant’s operation. Adequate protection can be achieved by installing backwater valves.
Wastewater from drainage systems
Under no circumstances may groundwater be discharged into the public sewerage system. If a building’s drainage system is to be connected to the sewerage network, the permissibility of such discharge must be agreed with the water authority or the sewerage network operator before construction begins. In this case, the drainage pipe must be routed into an accessible chamber with a sand trap at least 0.5 m deep, located outside the building, and connected to the drainage system in such a way as to prevent backflow. As the gradient to the sewer is usually insufficient, a lifting station must be used.
