Water stored in a copper container has health benefits. Your container needs daily care to prevent oxidation process of copper. It should be washed with a soft cloth and a metal cleaning agent like Pitambari, lime & salt, or vinegar & salt or tamarind. Wipe dry immediately or else water residues will leave stains. Some waters cause dark spots on copper. To remove, apply tamarind or vinegar or lime concentrate and leave for 15 mins. Wash off with clean water.