What exactly is hard water? Essentially it is water with a high concentration of minerals, especially calcium and magnesium. Although these minerals are not harmful for consumption, they can be a real annoyance in the home, as the calcium and magnesium tends to deposit on fixtures, shower doors, and tub walls, making cleaning day an even bigger hassle. Hardness is usually measured either in parts per million (typically abbreviated ppm) or more commonly in grains per gallon (gpg). Below, you can see water hardness represented throughout the United States:


