An ice maker includes a refrigeration system, a water system, and a control system. The control system includes an air fitting disposed in the sump of the water system, a pneumatic tube, and a controller including a processor and an air pressure sensor. The air fitting defines a chamber in which air may be trapped and includes openings through which water in the sump is in fluid communication with the air in the chamber. The pneumatic tube is in fluid communication with the air pressure sensor and the air fitting. The air pressure sensor is adapted to sense a pressure corresponding to a sump water level. The controller is adapted to control the operation of the refrigeration system and the operation of the water system based upon the sump water level and to detect one or more failure modes of the water system based upon the sump water level.