RSE = Backwater level
RSE = Backwater level
Determining the type of drainage
The position of the backflow prevention system in relation to the connected sewer is also a key factor in product selection. Wherever possible in the design, a sufficient gradient should always be established in accordance with the principle of gravity drainage. This enables drainage during normal operation without the need for additional pumping, thereby saving on investment, operating and maintenance costs. Both backwater valves and backwater pumping stations, as well as hybrid lifting stations, utilise this principle.
Gradient to the sewer: If the sewer lies below the backflow prevention device, domestic wastewater is discharged via the natural gradient. Backwater valves and hybrid lifting stations can be used here.
According to DIN EN 12056-4:2001-01, Section 4, backwater valves may only be used if:
- there is a gradient towards the sewer
- the rooms are of secondary use, i.e. no significant property or the health of the occupants would be compromised if the rooms were flooded
- the number of users is small and a toilet is available to them above the backwater level
- the drain point can be avoided in the event of backwater.
Determining the utilisation rate
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.
Operational safety in the event of a pump failure
Hybrid drainage systems (backwater pumping stations, hybrid lifting stations) offer 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 the shut-off device close, and drainage then takes place via the integrated pump.
It is possible to do without using a drain
- in domestic settings, if the drain point is not used and, regardless of this, a toilet facility is available above the backwater level
- in the case of wastewater containing mineral oil, provided there is no risk of stored light liquids escaping
- for Grease wastewater, provided that 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 doubles the operational reliability.
