Abstract: A water supply sub-system for connection to a main water supply system, in which the sub-system includes: a storage tank having an inlet for connection to the main water supply system, an outlet and an outlet line connecting the outlet of the storage tank to a pump which pumps water from the tank to a sub-system supply line. One or more branch connections are connected to the sub-system supply line. Connectable to the one or more branch connections are one or more high-demand water using devices, such as dialyzer re-use machines. The subsystem may feed water to these high demand devices, and the sub-system and the one or more high demand devices may thus be substantially isolated from the main water supply system so that the high demands thereof will not adversely impact the water supply parameters. Thus, one or more lower demand machines, such as dialysis machines, may be connected to the main line without supply parameter disruption thereto.