A suction pump unit has a negative pressure connection, a positive pressure connection, and a switching valve (2). The switching valve (2, 9) has a valve body with two inlets (22, 23), a first (22) of which is connected to the negative pressure connection and a second (23) of which is connected to the positive pressure connection. The switching valve (2) further has an outlet (26) with a through-opening, said outlet (26) being movable relative to the inlets (22, 23) from the first inlet (22) to the second inlet (23) and back, whereby the through-opening alternately forms a fluid-communicating connection with one of the inlets (22, 23). The through-opening of the outlet (26) is released and ventilated during at least one part of the movement between the two inlets (22, 23). The suction pump unit allows a passive and active ventilation of an outlet line (4) connected to the outlet (26).
