A multi-ported vessel system includes an outer pressure vessel containing a plurality of flow distribution tubes, each of which comprises a plurality of reverse osmosis membrane elements aligned serially within each tube. The outer pressure vessel includes bypass flow paths whereby feed water flows around each of the tubes within the vessel. Slots are disposed in the flow distribution tubes at the upstream end of each RO membrane element such that feed water reaches all RO membrane elements of the tubes in parallel. The serial alignment of the membranes also allows for serial water processing also. A product water tube collects the purified water from the reverse osmosis elements and provides it to a product water port. Brine water is provided to an output port to be discarded of for further processing. The parallel processing of feed water by all membrane elements results in increased productivity and reduced costs.