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M=
any industrial and domestic water users are concerned about the hardness of=
their water. Hard water requires more soap and synthetic detergents for ho=
me laundry and washing, and contributes to scaling in boiler and industrial=
equipment. Hardness is caused by compounds of calcium and magnesium, and b=
y a variety of other metals. Water is an excellent solvent and readily diss=
olves minerals it comes in contact with. As water moves through soil and ro=
ck, it dissolves very small amounts of minerals and holds them in solution.=
Calcium and magnesium dissolved in water are the two most common minerals =
that make water “hard.” =
The hardness of water is referred to by three types of measurements:=
grains per gallon, milligrams per liter (mg/l), or parts per million (ppm)=
. Milligrams per liter and parts per million are roughly equal in water=
analysis, whereas one gpg is equivalent to 17.1 ppm or mg/l. The water produced by the City of Maryvill=
e is considered “soft” according to the U.S. Geological Survey =
classification shown below. |
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Often, when you purchase =
a new dishwasher or washing machine, the manufacturer has recommended setti=
ngs that depend on the hardness of the water. The typical range of the mont=
hly average hardness for water delivered to your home from the City of Mary=
ville Water Filtration Plant is: January through June – 29 to 45 mg/l July through December - 44 to 55 mg/l The Environmental Protect=
ion Agency (EPA) establishes standards for drinking water which fall into t=
wo categories - Primary Standards and Secondary Standards. Primary Standard=
s are based on health considerations and Secondary Standards are based on a=
esthetics such as taste, odor, color, or corrosivity. There is no Primary o=
r Secondary standard for water hardness. In fact, the National Research Cou=
ncil (National Academy of Sciences) states that hard drinking water general=
ly contributes a small amount toward total calcium and magnesium human diet=
ary needs. They further state that in some instances, where dissolved calci=
um and magnesium are very high, water could be a major contributor of calci=
um and magnesium to the diet. (National Research Council, Drinking Water an=
d Health, Volume 3, National Academy Press, Washington, D.C., 1980). |
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