This invention provides an arrangem

This invention provides an arrangement for delivering purified water on demand, which includes a reverse osmosis filter having an inlet for connection to a source of pressurized water, and a purified water outlet connected to a tank where the purified water enters a bladder. Unpurified water from the filter is connected to the tank on the outside of the bladder for forcing purified water through a purified water outlet. This connection also includes a restricted passageway to a drain. A second discharge for unpurified water from the reverse osmosis filter connects through another restrictor to the drain. The system is controlled by an actuator which operates a valve to control the flow of unpurified water, thereby causing the same to force purified water from the tank to the purified water outlet, and a valve for controlling the flow of inlet water to the reverse osmosis filter, shutting off such flow when the tank is filled with purified water.