Mix 2 teaspoons of citric acid with 7 fl. oz. of water. Pour it into the empty sterilizer. Do not put the lid on. Switch on for 1-2 minutes. Switch off at the household power and leave it to stand for 30 minutes. Drain and rinse the inside of the unit. Then run a full cycle with baskets/racks inside and the lid on using 3 fl. oz. of water.
Pour 3.5 fl. oz. of white vinegar mixed with 7 fl. oz. of cold water into the sterilizer. Allow to stand in the unit until lime scale has dissolved – DO NOT SWITCH ON - Drain and rinse unit. Run a full cycle with baskets/racks inside and lid on using 3 fl. oz. of water.