Abstract: An inverted, displacer type piston pump for metering and dispensing liquids in which the cylinder is located beneath the piston and reciprocated via an actuator below the cylinder, and where the piston is held fixed. The liquid ingress and egress to and from the cylinder of the pump is via a cylindrical port through the piston along its cylindrical axis. The pump is designed so that liquid product loss through the pump is prevented without the use of elastomeric or compliant seals in the liquid contact product areas of the pump. In addition, the pump cylinder is capable of being positioned via its reciprocating actuator such that all of the liquid product contact parts are open and accessible to cleaning and sterilizing fluids which may be introduced into the pump through the liquid product supply port of the pump, thereby enabling cleaning and sterilization of the pump without its disassembly.