Abstract: The problem of minimizing size and weight parameters in an impeller-type centrifugal pump system (10), including a liquid ring priming pump (32), is solved by providing a housing (12) defining a fluid inlet (26). An impeller (16) is rotatably mounted downstream of the inlet on a rotatable shaft (18). A pressure balance chamber (42) is located behind the impeller to provide for thrust balancing of the impeller. A first passage (44) extends directly through the impeller communicating inlet pressure with the balance chamber. The first passage has an inlet forward of the impeller blades. The liquid ring pump is rotatably mounted on the shaft and is located behind the balance chamber. A second passage (46) communicates the inlet pressure in the balance chamber with the liquid ring pump outside the rotating shaft.