A pump section (4) has an impeller (2) located on a shaft (3). The self-priming mechanism section (5) has a self-priming chamber (12) located on the discharge side of a turbulence chamber (10) of the impeller, and is in flow connection with the discharge aperture (11). An intake chamber (14) on the intake side of the turbulence chamber is in flow connection with an intake aperture (13). A sealing wall near the discharge side of the turbulence chamber forms a narrow gap along the outer impeller circumference. A circulation aperture (19) in the self-priming chamber is located inside the outer circumferential circle of the impeller.
