A reciprocating pump comprises a cylinder, an inlet check valve, a piston, an outlet check valve and a purge circuit. The cylinder has a first end and a second end. The inlet check valve is disposed proximate a first end of the cylinder. The piston is disposed within the cylinder between the inlet check valve and the second end. The outlet check valve is disposed within the piston. The purge circuit extends across the inlet check valve and the outlet check valve to fluidly couple the first end and the second end.