Unold 18116 Notice D'utilisation page 13

3. To descale the kettle, fill it no more than
half full with a solution of half water and
half household vinegar. Bring the liquid to
a boil and leave it in the kettle for a while.
4. Pour the descaling solution out of the kettle.
5. Then fill it with fresh water and bring to a
boil. Pour this water out as well. Then rinse
the kettle at least twice with clear water.
6. Of course, you can also use commercially
available descaling products; please follow
the instructions on the package.
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