Mix up a solution of one part malt vinegar to one part water and pour enough into your kettle to just cover the element. Bring to the boil and leave overnight. Then rinse out.
Or, boil water in the kettle and then add 13 teaspoons/75g citric acid granules. Leave for 20 minutes, then rinse.
Or, use a chemical descaler. Read the manufacturer's instructions first.
