The term “water hardness” originally referred to the ability of water to precipitate soap and form soap scum. Soap is precipitated (or brought to the “surface”) by water containing high levels of calcium and magnesium. The “harder” the water the less soap will dissolve in the water.
In current practice, total hardness is defined as the sum of the concentration of the calcium and magnesium ions, expressed as calcium carbonate. Hardness can be expressed as calcium carbonate in either parts per million (the same as milligrams per liter) or grains per gallon. Since automatic water softeners are rated in grains of hardness removal, this is the more common measurement used by U.S. consumers. One grain of hardness equals approximately 17.1 ppm of calcium carbonate hardness.
Water hardness minerals can be removed by automatic water softeners, reverse osmosis or ultrafiltration systems. For residential and commercial applications these are the most effective. There are many devices on the market that purport to eliminate the effects of water hardness by the use of electrical fields, magnetism, or cataltyic metals. All these devices claim to reduce the effects of the hardness minerals and eliminate the effects of scale and build-up in piping and appliances such as water heaters. Most consumers however report little change and the claims of these manufacturers are not independently verified by recognized testing authorities such as National Sanitation Foundation or Underwriters Laboratories.
Natural waters may range from close to zero hardness to many hundreds of parts per million. In our experience, water over 100 or 150 ppm (approximately 8 – 10 grains/gallon) is hard enough to warrant water softening. When the water hardness exceeds 250 – 300 ppm, a water softener becomes somewhat of a necessity, as piping systems, water heaters, fixtures and appliances become scaled up and worn out prematurely. At levels of 100 to 250 ppm (or up to 8 to about 15 grains/ gallon) water softening is an aesthetic improvement, reducing spotting of fixtures and surfaces, and making hair and skin softer. Most facilities such as commercial launderers, hospitals and hotels use water softening to reduce costs and extend the life of equipment and laundered items. Levels of hardness above 100 to 250 ppm, depending on the water chemistry, makes water softeners economically feasible, saving piping systems, and dramatically extending the life of fixtures, appliances, and water heaters.