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What is that scum on the top of my cup of tea/coffee?

Naturally occurring minerals in the water can sometimes appear as a thin layer on your drink

Sometimes when you make a hot drink such as tea of coffee, you'll notice a thin layer of sediment floating on top of your drink. This is due to permanent hardness which contains the sulphates of calcium and magnesium, which remain insoluble even when heated. This mineral content of the water may form as grainy deposits. They are often white, but can be stained by the tea or coffee granules. These are just naturally occurring minerals so are not harmful to your health. You can use our postcode search to find out more about the hardness of your water.

If you'd like more advice or are at all concerned, call us on 0800 783 4444.