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.