Hidrostal Screw centrifugal pumps sized for a vacuum sewage pump system. This application required pumps that combined solids handling capabilities with low NPSH required characteristics. The design of the Hidrostal pump and impeller allow them to be used in applications where many other centrifugal solids handling pump cannot operate due to their unique 'Net Positive Suction Head required' characteristics. This also allows these pump types to lift liquids at greater depths and with longer suction pipe lines or as in this case on a pump system which draws sewage from a vacuum sewage system collection tank.