Water is supplied from a mains water supply station (6) to a main supply- conduit (12) which feeds a plurality of regional supply networks (14,16,18), via respective pressure reducing valves (20, 22, 24), at respective regional pressures. Each regional supply network has a boundary value for a parameter related to a property of the water, which may be water pressure or concentration of a water treatment agent. Each network has a critical point at which the value of the parameter is deemed least acceptable. Water supply characteristics in respect of each regional supply network (14,16,18) are monitored and the water supplied into the main supply conduit is processed to ensure acceptable values of the parameter are maintained at each critical point. Processing of the water may comprise controlling the output of one or more pumps arranged to pressurize the water supplied into the main supply conduit (12), or it may comprise controlling the addition of water treatment agent. Moreover, the processing of the water may be dependent on any one or more of : time, hour of the day, season, ambient air temperature.