A manually-actuated, constant reduced-pressure apparatus for use with a reduced-pressure system for treating tissue at a tissue site includes a flexible, collapsible member that is operable to move between a compressed position and an extended position. The collapsible member may be disposed between a carrier member and a slider member that move between a compressed position and an extended position. The carrier member and slider member are urged away from each other by a constant-force biasing member, e.g., a constant force coil spring. As the apparatus moves from the compressed position to the extended position, a constant reduced-pressure is generated and delivered to a reduced-pressure port. Systems, methods of manufacturing a manually-actuated, constant reduced-pressure apparatus, and methods of treating a tissue site are also provided.