The Gaggia Classic RI9481/11 does not explicitly require the use of filtered water. However, it is recommended to always use fresh water and not to fill the water tank with stagnant water in order to avoid contamination. The use of filtered water can help to reduce limescale deposits and extend the service life of the machine, but is not mandatory. Unfiltered tap water from the city of Zurich can generally be used as long as it is fresh and changed regularly. Regular descaling and cleaning of the machine is important in any case to maintain its function and flavour.