A method of producing sterile water from raw water during a production cycle in a production plant P, including adding a disinfectant to the produced sterile water during the production cycle to permanently monitor the condition of the sterile water and/or the production plant, and determining and evaluating a reduction of concentration of the disinfectant directly in the production stream. In a production plant suited for carrying out the method, a sterile sensor is provided directly in the production stream through which the reduction of concentration of the disinfectant added to the produced sterile water can be permanently measured and evaluated to provide a sterility evidence.