A water distribution system including a water storage tank, a water treatment unit, a diverter valve, and interconnecting water conduits arranged so that the same water treatment unit can be used to treat water supplied from a fill port to the storage tank during a fill operation, as well as water leaving the storage tank for supply to one or more points of water use during a supply operation. A diverter valve is provided which is movable between a fill position wherein the water treatment unit is in fluid communication with the fill port and not the point of water use device, and a supply position wherein the water treatment unit is in fluid communication with the at least one point of water use device and not the fill port. When the diverter valve is in the fill position, water supplied to the fill port can thus flow through the diverter valve and to the water treatment unit for treatment then to the storage tank for storage. When the diverter valve is in the supply position, the water from the storage tank can be delivered using means for pressurizing water to the same treatment unit for treatment, then through the diverter valve and to the at least one point of water use device.