A more economical approach to develop high pressures with a single centrifugal pump is to include multiple impellers on a common shaft within the same pump casing. Internal channels in the pump casing route the discharge of one impeller to the suction of another impeller. The pump consists of a base and a pump head and chamber stack. The outer sleeves are secured between the pump head and the base by means of staybolts. The base has suction and discharge ports on the same level (in-line).