Abstract: The invention relates to a new water purification system design that uses reverse osmosis membrane filtration and optional ultra violet light treatment. The new system creates the potential for achieving a higher standard of performance for point-of-use reverse osmosis systems. The system provides for a multiple pass, multiple barrier method for delivering freshly treated, high-quality water from the system. A microprocessor controlled operating system maintains the system within a narrow range of optimal performance at all times. The system provides for two water storage tanks, each equipped with its own pump. With an operating system sequence of alternating flow cycles, an internal state of continuous water movement and dynamic treatment is created and maintained within the elements of the system. The system dynamics contribute to microbial control throughout the system. The system incorporates cross flow filtration in all elements.