Yes...I've had this one too. (a) learn to live with it. (Counteract the taste by adding evaporated milk to your tea/coffee) or (b) remove tank and plumbing and replace with new...or (c) remove tank and plumbing and flush with hot water and detergent, and then flush again with a commercial 'kettle scale remover'; flush again and leave tank full of fresh water over night - then replumb the whole system. But still use evaporated milkl for a few days. - Oh and make sure when you refit you give the fuel and water fillers distinctive colours - or a wide seperation.