The water specification is part of the appliance's operating design. Substituting distilled, softened, filtered or treated water is not automatically acceptable.
What the observation means
Different steam systems use different sensing and maintenance arrangements. A recommendation for another brand or an ordinary kettle cannot establish what your oven requires. The water-hardness setting, where provided, is also model dependent.
A useful next step
Use the exact manual's filling guidance and avoid adding fragrances, cleaners or cooking ingredients to the reservoir. If the wrong product was added, stop using the steam function and seek advice with its name and amount. Do not try to flush it through repeated cooking cycles.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.