Water hardness is caused by the presence of the dissolved minerals calcium and magnesium, often measured in grains per gallon of water (gpg). 

When you have high levels of calcium and magnesium in your water, basic household tasks become difficult -- more scrubbing power is required, and greater amounts of detergents are needed to clean fixtures, clothing, and appliances. 

How to Recognize Hard Water

The following are some of the tell-tale signs of hard water:

• Soap scum on bathtubs, shower tiles, and basins, reulting in additional scrubbing and scouring of fixtures; film left on the body that can leave your skin dry and your hair limp and dull. 
• Reduced sudsing and cleaning capabilities of soaps and detergents. Clothes appear dingy and yellowed, and soapy residue reduces the life of fabric, requiring use of more detergent to clean and extra rinse cycles to remove soap curd. 
• Clogged pipes or appliances, reducing water flow and increasing amounts of repair problems due to excessive wear on moving parts. 
• Increased water heating costs as a result of scale buildup and mineral deposits. 

The method used most often in homes to remove water hardness is ion exchange water softening, in which positively charged hardness ions (magnesium and calcium) are replaced with sodium or potassium ions. This exchange of hardness ions for sodium or potassium ions takes place in the resin bed of the treatment unit during the softening cycle. 

Benefits of Soft Water to the Consumer

• Extends the life of plumbing systems and water-using appliances through the reduction of clogging from scale within the pipes. 
• Reduces soapy residue on clothes, film on tub and shower tiles, and scratching on bathroom fixtures. 
• Heating efficiencies on hot water tanks using softened water can increase up to 29 percent. 
• Makes hair shinier and skin cleaner and healthier looking by reducing soap scum buildup. 

Automatic -- An automatic water softener is equipped with a clock timer that automatically starts the regeneration process at preset intervals. During the regeneration process, the hardness ions collected in the ion exchange resin must be flushed out in order to allow the continuous exchange between soft and hard ions. The entire softening process is controlled automatically by the clock timer.

Demand Initiated Regeneration (DIR) -- Demand initiated regeneration (DIR) is the most efficient type of automatic water softener. Instead of regenerating at a preset interval, a DIR unit regenerates only when soft water runs out. DIR units use sensors or valves to determine when to regenerate. Because they adjust to the amount of water actually used, DIR units consume up to fifty percent less salt and water than do preset time clock automatic softeners. 

Portable Exchange -- A portable exchange unit is a type of softener with a removable tank that is rented to a homeowner, and contains ion exchange resin that is fully regenerated and ready for use. When the resin material is exhausted (that is, when it is no longer exchanging hard ions for soft ions), the tank is returned to a central plant where it is regenerated and reprocessed to be used again.