an ink containment and dispensing device for an inkjet printer is provided with a main reservoir in the form of a flexible pouch panel , which is typically maintained at ambient pressure . the main reservoir is coupled to a variable volume chamber via a one - way valve which allows the flow of ink from the reservoir to the chamber and prevents the flow of ink from the chamber to the reservoir . the chamber is coupled to a fluid outlet , which is normally closed to prevent the flow of outward ink . however , when the ink supply is installed in a printer , the fluid outlet establishes a fluid connection between the chamber and the printer . the chamber is part of a pump provided with the ink supply that can be actuated to supply ink from the reservoir to the printer . the pump has a linearly acting pumping member and a flexible diaphragm that overlies the pumping member , the diaphragm being impervious to the transmission of oxygen and moisture therethrough to prevent degradation of the ink within the chamber .