Abstract: An automatic fluid dispenser includes a pump mechanism actuated by the movement of a piston between a first position and a second position. The piston includes a resilient diaphragm that separates a pump chamber from a pressurized fluid chamber. An inlet check valve in the pump chamber, biased into a closed position, allows fluid flow only into the pump chamber from a fluid source, and an outlet check valve allows fluid flow only out of the pump chamber. A valve in a conduit, coupling the pressurized fluid chamber to a pressurized fluid source, is movable between an open position in which the pressurized fluid moves the piston to the second position, dispensing fluid from the fluid chamber, and a closed position in which the pressurized fluid is bled from the pressurized fluid chamber and the piston returns to the first position, thereby drawing additional fluid into the fluid chamber.