1. The stormwater from the area to be drained is fed in at the lower end of the shaft. The water is tangentially deflected by the deflector.
2. Here, the sedimentation of particles and in particular the sand fraction takes place in a hydrodynamic separator on account of turbulent secondary flows in a radial laminar flow regime.
3. The particles are caught in a sludge trap underneath the system via an opening in the lower part of the cleaning shaft. The sludge trap is evacuated at intervals.
4. There are six filter elements in the center of the cleaning shaft, with which the fines are filtered in an upward flow process and the majority of the dissolved pollutants are precipitated and adsorptively bound. The filter can be backwashed from above and is easy to replace in case it is fully silted up.
5. The filter elements are easy to remove via the existing shaft opening.
6. The clean water is located above the filter elements; it passes through an oil separator and then flows via the outlet into the seepage or a surface water.