All in one” unit in a cabinet housing with lockable door and viewing window. All components (pretreatment, softening, reverse osmosis, pure water tank with level control and pressure increase) are integrated and pre-assembled ready for connection. Multilingual microprocessor control with LCD display for controlling and monitoring RO systems. Display of permeate conductivity, fully automatic rinsing cycles and potential-free fault messages. Subsequent modular capacity increase possible.