What is Hard Water?

Water in the home may be "hard" or "soft," depending on its mineral content. Water that contains more than one grain of calcium and magnesium per gallon is said to be 'hard."

• A grain is defined as a unit of weight equal to 1/7000th of a pound. Another way to think of it is that a common aspirin tablet is approximately 5 grains. A household with a water hardness of 10 grains per gallon would have the equivalent of the weight of 2 aspirin tablets dissolved per gallon of water.

  1 Grain = 1/7000 of 1 lb.
  An average household of 4, with water hardness of 7 grains per gallon, would have the equivalent of 146 lbs. of rock in their water supply in a given year.

Water is soft when it falls from the sky as rain. As it travels through rock and soil, it picks up particles of calcium, magnesium, iron, lead and other minerals. Unless you have a private well, your tap water is processed by a municipal water treatment plant to remove some of its mineral content and other impurities. Depending on the type and amount of processing, water softness will vary from place to place. Still, in most of the United States, water is relatively hard when it leaves the treatment plant.

 

US Water Hardness Map.