A drainage pump unit for aspirating body fluids comprises a suction pump housing and a suction pump arranged in the suction pump housing. A fluid collection container can be secured releasably on the suction pump housing. A flat band-shaped capacitive filling level sensor is arranged on the suction pump housing for the purpose of detecting a filling level in the fluid collection container. The drainage pump unit also comprises an elastically configured coupling element with a first surface and a second surface lying opposite the first surface, and the coupling element, in the secured state of the fluid collection container, bears with the first surface on the filling level sensor and with the second surface on an outer wall of the fluid collection container. By virtue of the elastically configured coupling element, this drainage pump unit permits a filling level measurement even in the case of low filling amounts.
