Hard water is simply water that contains two harmless minerals - calcium and magnesium. Water is considered "hard" if it measures more than 120 parts per million or 7.0 grains per gallon.
Although hardness does not affect the safety of the water, some customers may find it to be inconvenient. The minerals may make the water hard to develop a sudsy lather. Hardness minerals may also contribute to scaling in teapots, spots on dishes and residues on plumbing fixtures and glass shower doors.