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What Makes Water Hard,
and How Can it be Improved?
The most common water quality problem reported
by consumers is hard water. A 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 hygeine such as hair washing, or through the appearance
of fixtures and appliances or changes in heating costs.
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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.
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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.
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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.
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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 facilityis 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:
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Resin Tank - Contains the resin bed.
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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.
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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:
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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)
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The life of the plumbing system may increase
because clogging from scale within pipes will be reduced.
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Many appliances may last longer and perform better.
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Soapy residue on clothes is reduced so they may
look and wear better.
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Skin and hair can be rinsed more completely,
making hair look shinier and skin cleaner.
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Film on tubs and shower tiles may be reduced,
as will scratching to bathroom fixtures and sinks.
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