Abstract: A liquid metering flush valve to be installed in connection with plumbing fixtures such as water closets, urinals, service sinks, and other equipment and to supply said fixtures with a predetermined amount of water; which may be potable water, contaminated water, sea water, corrosive and/or unfiltered water, and water and/or oil combinations; at controlled pressures, flow rates and volumes. The basic valve design is on the hydraulic principal of proportional flow through orifices, regardless of pressure fluctuation but employs the use of four chambers, two of which are sealed and contain not only an orifice therebetween but a filtered, non-corrosive captive liquid to assure the orifice of protection from corrosive action and dirt which may damage the orifice or clog it and prevent it from working properly.