Exemplary two chamber foam pumps, refill units and dispensers utilizing the same are disclosed herein. An exemplary refill unit includes an inverted container having a neck located at the bottom of the container and a foam pump secured neck. The foam pump includes a first air pump chamber, a liquid pump chamber and a second air pump chamber. In addition, the pump includes a piston. The piston has a hollow central portion. A first air inlet aperture is located through a wall of the piston between the first air pump chamber and the hollow central portion. A liquid inlet aperture is located below the first air inlet aperture and between the liquid pump chamber and the hollow central portion. A second air inlet aperture is located through the wall the piston located below the liquid inlet aperture and between the second air pump chamber and the hollow central portion.