A vortex brake (4) for a liquid drainage system has a vortex chamber (5), an inlet section (6) and an outlet (12), wherein liquid can flow into the inlet section (6), through this into the vortex chamber (5), through this and out through the outlet (12). The vortex chamber (5) has a side wall (9), following a conical face, and a base wall (11). The conical face has a cone axis (10), and the outlet (12) is located at an apex of the conical face. The inlet section (6) has side walls (14) and a bottom wall (15) that extend mutually in parallel in a direction of flow (16) in the inlet section (6), and a ceiling. Said ceiling having a converging ceiling portion, which extends between a first and a second end of the ceiling portion, and which, in said direction of flow, extends converging towards the bottom wall (15).