Water quality is of central importance when reprocessing medical devices. We recommend using fully desalinated water and check and document the quality of the water for interim and final rinsing in washer-disinfectors and EWDs. Poor water quality poses potential hazards and risks such as calcium deposits or pitting. High water quality helps ensure material integrity of instruments helps with long-term maintenance of washer-disinfectors/ EWDs. Test strips or electronic testers can be used to measure electrical conductance and water characteristics such as pH value and hardness. Water parameters are specified in DIN EN ISO 15883 Part 1 Washerdisinfectors and DIN EN 285 Steam sterilisers (for boiler water).