An air driven liquid pump includes a reservoir, a liquid inlet aperture extending through the reservoir wall for fluid coupling to a liquid inlet duct, a liquid outlet aperture extending through the reservoir wall for fluid coupling to a liquid outlet duct. The liquid outlet aperture is in fluid communication with an outlet level inside the reservoir chamber located below the liquid inlet aperture and corresponding to a predetermined lower threshold value of the volume of the liquid within the reservoir chamber. The liquid pump also includes an air aperture extending through the reservoir wall for pneumatically coupling the reservoir chamber with the atmospheric air located exteriorly to the reservoir, a liquid inlet valve operationally coupled to the liquid inlet aperture and an air valve operatively coupled to the air aperture. A volume responsive first actuating mechanism is provided for selectively moving the liquid inlet valve to the liquid valve closed configuration and the air valve to the air valve open configuration upon the volume of liquid within the reservoir reaching a predetermined upper threshold value. A volume and pressure responsive second actuating mechanism is provided for selectively moving the liquid inlet valve to the liquid valve open configuration and the air valve to the air valve closed configuration upon the volume of liquid within the reservoir reaching the predetermined lower threshold value and the pressure differential between the air pressure inside and outside the reservoir reaching a predetermined differential threshold.