All in one” unit for space-saving integration in a 90s substructure. All components (pretreatment, reverse osmosis, electrical deionization, storage tank with level control and pressure increase) are integrated and pre-assembled ready for connection. Multilingual microprocessor control with graphic display for controlling and monitoring pure water systems. Display of permeate and pure water conductivity as well as tank volume display in%. Subsequent modular capacity increase possible.