A piston type pump includes a pump housing having at least one pump inlet, at least one pump outlet, and a piston arrangement connected to a drive shaft configured to, when driven, set the piston arrangement into movement. The piston arrangement includes a first primary stage piston, the first primary stage piston being slidably seated in a first primary stage cylinder formed in the pump housing, and a first secondary stage piston. The first secondary stage piston is slidably seated in a first secondary stage cylinder formed in the first primary stage piston.