This is just the natural calcium and magnesium salts (carbonates) coming out of solution. You must be living in an area with 'hard' water, so perhaps an area with chalk or limestone geology. There is no health risk associated with hard water. Regards Harriette
The carbonate residue (also known as "furring") occurs in most hot water systems and if allowed to build up too much makes the heating process very inefficient. It can be removed from cooking or heating utensils by soaking in a weak vinegar or lemon/ orange juice solution overnight - and rinsing well afterwards! Regards, Leigh
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