The pumping device comprises a pump (17) driven by a motor (18) having a stator (19) and a permanent-magnet rotor (22) located between polar expansions (21) and connected to an impeller (23). A liquid suction duct (14) and a liquid delivery duct (15) are connected to the pump (17) to define a hydraulic circuit. A reciprocating vacuum pump (25), for creating a negative pressure at the suction duct of the pump (17), has a resilient cylindrical element (33a) connected to a rigid cylindrical box-like element (34) and defines therewith a chamber (33). The chamber (33) has inlet and outlet valves (38,39) connected to the hydraulic circuit through a poppet valve (27), and an arm-like member (41) connected to the resilient element (33a). An opposite end of the arm-like member (41) supports a magnet (42) located between poles (21) of the stator (19) of the motor (18), whereby to cause movement of the arm-like member (41) and the resilient element (33a) for circulating fluid through the chamber (33) via the inlet and outlet valves (36,39) for priming the pump (17) upon actuating the poppet valve (29).
