A water supply system (1) includes an electric motor (8) and a centrifugal pump (7) which is driven by the electric motor (8) and with at least one impeller (10) which produces a main delivery flow (29) through an annular space (12) as well as a cooling fluid delivery flow (30) through a space (28) surrounding the motor (8). The annular space (12) is divided by two guide vanes into part-annular-spaces (23, 24) which have a different pressure level on operation. Each part-annular-space (23, 24) is conductively connected to the space (28) which surrounds the motor (8) and through which the cooling fluid runs (FIG. 5).