An ink jet printhead cartridge includes a cartridge body including a base and a plurality of side walls extending upwardly from the base. A filter tower having a tower wall has an interior surface that defines a location of a tower passageway. A printhead chip assembly is attached to the base of the cartridge body in fluid communication with the tower passageway. A filter is attached to the filter tower at a distal end thereof. An ink fill access port is formed through a side wall of the plurality of sidewalls, and through the tower wall of the filter tower, to define a fluid path from the atmosphere external to the cartridge body to the tower passageway of the filter tower to facilitate the injection of ink directly into the filter tower during an ink filling operation for the ink jet printhead cartridge.