Hardness
Water hardness is a combination of the water's Calcium and Magnesium levels. 'Hardness' = (Calcium x 2.5) + (Magnesium x 4). While many bottled waters are naturally soft, town supplies tend to be relatively hard. Hard water is the primary cause of scale. Hence, water authorities often 'soften' water supplies with the addition of Sodium (salt). Bottled waters may also sometimes be softened through the addition of Oxygen.
