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 .