Mixing a pumped fluid with a lubrication fluid within a pump can undermine the lubricity of the lubrication fluid. In order to reduce mixing of fluids within a pump of the present disclosure, a pump is provided that comprises a housing, a piston, a first annulus, and a second annulus. The housing includes an inlet for the pumped fluid, an inlet for the lubrication fluid provided at a first pressure, and a piston bore fluidly coupled to the inlet for the pumped fluid. The piston is moveable within the piston bore. The first annulus is fluidly coupled to the inlet for the lubrication fluid. The second annulus is configured to be fluidly coupled to a drain circuit provided at a second pressure less than the first pressure. The first annulus and the second annulus are located along the length of the piston bore.