A suction pump unit comprises a vacuum port, an excess pressure port and a switching valve. The switching valve comprises a valve body with two inputs, wherein a first of the inputs is connected with the vacuum port, and a second of the inputs is connected with the excess pressure port. The switching valve further comprises an output with a through hole, wherein the output can be moved relative to the inputs from the first input to the second input and back, as a result of which the through hole alternately establishes a fluid-communicating connection with one of the inputs. The through hole of the output is released and ventilated during at least part of the movement between the two inputs. This suction pump unit permits passive and active ventilation of an output line connected with the output.
