It’s good to know that a BOROUX water filter doesn’t completely remove calcium from the water. Larger amounts are reduced, and synthetic calcium is removed. However, a BOROUX water filter retains beneficial minerals (those that occur naturally in water and are good for human health) in the water. And calcium is one of these. So you retain the mineral calcium in the water, and this can still cause some scaling. In short, a BOROUX water filter is not designed to remove all the calcium from the water.