Tech Papers | What Makes Water Hard, and How Can it be Improved?

What Makes Water Hard  
& How Hard Water Can Be Improved 

The most common water quality problem reported by consumers throughout the U.S. is hard water. A U.S. Geological Survey indicates that hard water is found in more than 85 percent of the country. So then, what makes water hard, and what can consumers do to treat this problem?  

Hard Water

Because more than 60 percent of the earth's water is groundwater, it travels through rock and soil picking up minerals, including calcium and magnesium along the way. These two contaminants produce what is commonly referred to as "hardness" in water. Generally speaking, hardness is measured in grains per gallon (GPG). For example, if a water test indicates a range of 1.0 to 3.5 GPG, the water is considered slightly hard. If the measurement is greater than 10.5 GPG, the water is rated as being very hard.  Hard water can be detected easily, even as one performs personal hygiene such as hair washing, or through the appearance of fixtures and appliances or changes in heating costs.  

• Clogged pipes and/or appliances could be a sign of hard water. Hard water mineral deposits can form in coffee makers and can build up in pipes or plumbing equipment. A consumer may notice a reduced water flow, as well as an increase in the number of calls to a repair person. 

• Consumers may notice a film on their bathtubs or shower tiles, or even on themselves. The film that is left often results in additional scouring and scrubbing of the affected fixtures, and can cause hair to be dull and limp, and dry the skin. 

• A consumers water heating costs could increase as a result of hard water. When hard water is heated, the minerals can precipitate and form scale. Besides buildup, mineral deposits can form an insulating barrier between the heating element and the water to be heated. 

• The calcium and magnesium in hard water act on many soaps and detergents to reduce their sudsing and cleaning capabilities. The soapy residue they form can be abrasive and reduce the life of clothing. 

In areas where the water is hard or very hard, the local water utility may soften the water to about 5 or 6 gpg. This figure is still considered moderately hard, and consumers may still wish to soften the water further. The most common option for consumers is ion exchange water softening in the home. Domestic softening makes economic sense because it only softens the water to be used for laundering, cleaning, and other home uses. Softening at the central treatment facilities costly because it softens all water, including that which is used for fighting fires and cleaning streets.  

Water Softening

There are many different types of softeners, each with its own benefits. The method used most often in homes is cation exchange, the principles of which are simple. An ion is an electrically charged atom or group of atoms. A cation is a positively charged ion. The water is softened when the hardness ions (magnesium and calcium) are exchanged for sodium ions. This exchange occurs in a resin bed during the softening cycle.  

Three main parts make up most water softeners:  

• Resin Tank - Contains the resin bed. 

• Resin Bed - This is made up of tiny bead-like material often made of styrene and divinylbenzene. The beads attract and hold positively charged ions such as sodium, but will exchange them whenever the bead encounters another positively-charged ion such as calcium or magnesium. 

• Brine Tank - This tank holds the dissolved salt solution that is necessary to regenerate the resin. Regeneration refers to reversing the ion exchange operation. The magnesium and calcium ions are driven off of the resin beads and replaced by positively charged sodium ions. The regeneration occurs when the resin beads are washed with a strong salt water solution. The salt forces the calcium and magnesium ions to be released, and they are then discharged as waste during the backwashing cycle. The beads are ready to once again attract hardness ions from the water. 

Many installed water softeners are fully automatic. An automatic unit regenerates according to a preset clock. For example, it might be set to regenerate every third night at 3am. Other systems may use an electronic sensor that regenerates the system according to water usage.  

Size and Type Considerations

When water softeners were first manufactured, manual and semi-automatic models, where the regeneration process was started "manually" by the homeowner, were the most common types sold. Today, the two main types on the market are automatic and demand-initiated regeneration (DIR) water softeners. Automatic softeners regenerate on a schedule regulated by a timer. DIR softeners are the most sophisticated, containing a hardness sensor or water meter which triggers regeneration as needed.   There are several factors that a person must take into consideration before purchasing a softener, including the number of people in the home, how much water is used, and the hardness of the water.   Determining the size of the softener, knowing these factors, is rather simple. Multiply 75 (average gallons per day used per person) by the number of people in your household. For example, four people in a household will likely use 300 gallons of water per day. Multiply the 300 gallons per day by the number of grains per gallon of hardness present in your water. Continuing the example, 300 gallons per day times 20 gpg gives a figure of 6000 grains of hardness per day that would require removal. Given a typical regeneration capacity of 18.000 to 30,000 grains per regeneration, a softening system in this case would optimally be regenerated every three to five days.  

The Sodium Issue

For some consumers, the fact that sodium is used to soften water raises a concern about their drinking water and a potential health risk. However, what many people may not know is that when doctors and researchers discuss salt and its effects on a person's health, they usually refer to sodium chloride, and not sodium bicarbonate which is the result of softening.  Further, according to Dr. Andrew Zeifer, Director of the Hypertension Clinic at the University of Michigan, "Drinking water represents a very small part of sodium intake in most persons. Even water softening systems using salt don't introduce enough salt to be of concern." Similar view were expressed in the New England Journal of Medicine, and by the U.S. Environmental Protection Agency.  

If consumers do not want to add any additional sodium to their diet, or if they are on a medically prescribed diet, they may choose to connect their water softener to the hot water line only, thus leaving consumers able to drink and cook with unsoftened cold water. Another option would be to install a reverse osmosis or distillation system, and have the full benefits of both technologies in their home.

Benefits of Softened Water

Even for those whose water is slightly hard, significant benefits can result from using softened water:  

• Water heating efficiencies on systems using softened water may be increased up to 29 percent if heating with gas, and 22 percent if using electricity. (Source: New Mexico State University Study) 

• The life of the plumbing system may increase because clogging from scale within pipes will be reduced. 

• Many appliances may last longer and perform better. 

• Soapy residue on clothes is reduced so they may look and wear better. 

• Skin and hair can be rinsed more completely, making hair look shinier and skin cleaner. 

• Film on tubs and shower tiles may be reduced, as will scratching to bathroom fixtures and sinks. 

A final tip: Look for the WQA Gold Seal on home water treatment systems. This recognizable symbol gives the consumer the assurance that the equipment has been tested against industry standards, and successfully passed these tests, and has been validated for performance capabilities.    

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