An inkjet printer includes a printhead for printing onto a media substrate, the printhead defining a plurality of nozzles from which ink is expelled; an ink tank provided upstream of the printhead; a sump provided downstream of the printhead for collecting unused ink from the printhead, the sump having a lower portion for holding the unused ink and an upper portion defining a headspace of air above the unused ink; a first fluid conduit extending between the printhead and the sump for communicating the unused ink from the printhead to the sump, the first fluid conduit connecting the sump to a position in the printhead upstream of the plurality of nozzles; and a pump connected to the sump, the pump for drawing air from the headspace of the sump into atmosphere and effecting a negative pressure in the printhead upstream of the nozzles. Communication of ink from the ink tank to the printhead is effected by the negative pressure generated by the drawing of air from the headspace of the sump.