Question submitted by Karen Dover.
Hard water is water that contains calcium and magnesium salts dissolved in it.
These salts make it difficult to get soap to lather, can leave deposits on cloths that were washed in hard water, and can also leave deposits in water pipes. Soft water does not contain these salts, and the problems associated with hard water are not present. Water softeners run hard water through a filtration system to remove the calcium and magnesium salts from the water to change it from hard to soft.