RSE = Backwater level
RSE = backwater level
RSE = backwater level
How do you determine the backwater level?
The first step is to determine whether a backflow prevention device is necessary. The first task is to establish the backwater level. Technically speaking, the backwater level may be specified by the local authority. However, this does not exempt the designer from conducting a detailed assessment of the local situation, taking into account the physical principle of communicating vessels. As a result, the backwater levels may turn out to be quite different.
If no information is available, the following applies:
- On level ground: the road surface including the pavement or verge (DIN-EN 12056)
- On sloping terrain: 15 cm above the level of the nearest manhole viewed against the direction of flow (Ö-Norm B2501)
- For connected collection pits: the upper edge of the cover
KESSEL recommendation – Keep a safe distance!
Always plan the safe backwater level with a safety margin relative to the physical backwater level!
- Physical backwater level
Static distribution of water due to communicating pipes - Safety margin
Required distance between the physical backwater level and the backwater level - Assumed backwater level
Dynamic distribution of water due to backwater pressure and inflow
1: +15 cm safety margin
2: Physical backwater level
safe distance
What other regulations stipulate in this regard.
Austria: ÖNORM B 2501 = 15 cm
Switzerland: SN 592 000 = 10 cm
Various local regulations = 10 to 30 cm
DIN EN 12056-4: “Road
surface is the carriageway including pavements and verges” (this corresponds to approximately 15 cm)
Therefore: KESSEL recommendation for a safe backwater level = Physical backwater level = top of the road plus a 15 cm safety margin
Relevant level
The next step is to determine the relevant level at the drainage points as a reference value. The following applies:
- for waste water outlets, the water level in the trap
- for rainwater, the upper edge of the drainage point (cover)
And in the next step, it must be determined which of these drainage points lie below the backwater level and therefore require protection.
For wastewater drainage points, the height of the odour trap (GVH) is decisive. This must be compared with the backwater level (RSE).
