If it is not possible to do without a drainage point, the downstream backflow prevention system must ensure that drainage is still possible even during a backwater situation. This therefore requires the pump to be in operation. The pump must either drain via the backwater loop or against the backwater into the drainage pipe.
Hybrid drainage (backwater pumping stations and hybrid lifting stations) offers even greater operational reliability in the event of a pump failure, as drainage continues provided there is sufficient gradient to the sewer. This means no pump energy is consumed. Only when backflow occurs does a motor-driven shut-off device close, and drainage then takes place via the integrated pump.
It is not necessary to use a drainage point:
- in domestic settings, if the drain outlet is not used and, regardless of this, a toilet facility is available above the backwater level
- in the case of waste water containing mineral oil, provided there is no risk of stored light liquids escaping
- in the case of Grease wastewater, if kitchen operations can be suspended
In particular, for lifting stations, a dual-pump system with two pumps of equal capacity must be installed in accordance with DIN EN 12050-1 or DIN EN 12050-2, depending on the application, if the wastewater flow must not be interrupted. The second pump improves operational reliability.
Which pumps are suitable for which type of application?
For backflow prevention systems with pressure drainage (lifting stations, small lifting stations, pumping stations, backwater pumping stations), it must be determined, depending on the type of use, whether continuous pump operation is required or whether drainage can be carried out in batches. To this end, it must be assessed how frequently and in what volumes wastewater is discharged via the backflow prevention system.
Pumps operating in mode S1 (continuous operation) are used for the disposal of large, continuously occurring volumes of wastewater. In operating mode S3 (intermittent operation or periodic start-stop operation), the maximum operating time of the pump is limited to a certain proportion per 10 minutes (specified as a percentage or in minutes). This proportion results in correspondingly different pumping capacities for such pumps.
