Dispensers, refill units and pumps are disclosed herein. The refill units include a container secured to a pump. Some exemplary refill units for dispensers include a container for holding a liquid and a post seal pump. As the post seal pump operates, a piston moves up and down over the pump seal. When the piston shaft is in a first position, fluid flows into the pump chamber and one or more apertures through the piston shaft are sealed off by the post seal. When the piston shaft is in a second position, the piston engages a wall of the pump chamber and the one or more apertures are away from the post seal to provide a fluid path from the pump chamber to the interior of the hollow piston shaft and is dispensed through an output.