Abstract: The invention generally relates to refillable ink cartridges for computer controlled ink jet printers and, more specifically, to apparatus for refilling collapsible ink bags which are maintained at sub-atmospheric pressure within such equipment. The refilling apparatus includes a fluid bridge located between the reservoir holding replenishment ink and the ink cartridge. The fluid bridge may contain either a purge valve and/or a priming valve that prevent air bubbles from being introduced into the ink bag and from obstructing the flow of replenishment ink.