As water falls from the sky in its various forms, it absorbs carbon dioxide in the air and becomes slightly acidic. Water in this weak acid state reaches and enters the ground. Since it is acidic, it absorbs calcium and magnesium, among other things, from the layers of rock through which it passes. The minerals neutralize the water's acidity but also make it hard. Then the water finds its way into larger bodies of water both above and below ground, and eventually into our homes.
Most homes use water that is considerably harder.
While many families choose to soften their water by removing the calcium and magnesium with home water treatment equipment, many don't even realize they have hard water. Probably the most recognizable symptoms of hard water are soap scum in the tub and shower, and hard water spots on faucets and fixtures. According to an Ohio State University study, the average person cleaning a home spends more than six hours a month cleaning tap water spots, streaks and scum alone. Hardness minerals react with soaps and detergents to form an insoluble, sticky residue that's difficult to rinse from bathtubs, sinks, faucets and fixtures. The same soap residue is often left on hair, skin and clothing, too.