A pump apparatus is provided which comprises a first displacement pump and a ceramic valve construction formed of a ceramic rotor, a ceramic stator having flat surfaces which are positioned in sealing relationship and a second displacement pump having check valves. The first displacement pump comprises a reciprocating first piston within a housing having an interior wall spaced apart from the piston. The position of the first piston and the position of the rotor are controlled to effect desired fluid flow through the stator. The first piston and a second piston of the second displacement pump are reciprocated by a common motor.