The Waterous CPK-5 is a two-stage, iron-body centrifugal pump designed for Ultra-High Pressure (UHP) applications on Aircraft Rescue and Firefighting (ARFF) vehicles, specifically integrated into the ... The Waterous CPK-5 is a two-stage, iron-body centrifugal pump designed for Ultra-High Pressure (UHP) applications on Aircraft Rescue and Firefighting (ARFF) vehicles, specifically integrated into the 2016 Oshkosh fire truck platform. The specific build for serial number 156882 requires a pump with a rated capacity of 320 GPM at 1350 PSI, a clockwise input rotation, and an inverted transmission mounting configuration.