Abstract: A method is provided for the continuous production of treated waters using a staged, tapered array membrane plant by a process of process-logic-controlled (PLC) stage or stage increment isolation and removal from service, washing and return-to-service concurrent with the continued operation of all other stages and/or stage increments of the plant. Specifically, there are plant mounted input/output sensors that supply the PLC with the data required to identify the location and degree of “fouling” of the individual stages or stage increments of a tapered array membrane water treatment plant, where fouling is defined as a loss of water flow through a membrane surface at a given pressure when compared to a water flow standard for the surface.