The recirculation pumps of brake systems with a precharging device are subject to heavy loads from the precharging pressure and are subject to premature wear. Over time, significant leakage occurs which, in the worst case, damage the pump motors. Therefore, the invention proposes regulating the pressure medium supply from the precharging source (4) to the suction side of the recirculation pump (21) in relation to the pressure differential in this connecting line (22). For this purpose, an electromagnetically activated on-off valve (23) with a hydraulically insertable throttle element (52) is proposed.