Abstract: A manually-refillable water reservoir assembly, which may be retrofit to a post-mix beverage dispenser to supply water from the reservoir instead of from a commercial water supply, includes a manually-refillable water container which plugs into a base assembly. The base assembly includes a socket for receiving the container, a centrifugal pump and a water filter. The beverage dispenser contains a turbine-type pump for supplying water to a carbonator at a predetermined pressure and flow rate. The inherent slippage in the centrifugal pump permits the flow rate and pressure of water supplied to the dispenser to adjust to that of the turbine-type pump.