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Water Hardness

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Water hardness is due to the presence of certain dissolved minerals, calcium and magnesium compounds, which give the water two-well-known characteristics: the minerals will react with soap to produce a sticky, gummy deposit called "soap curd," and when the water is heated, the minerals can form a hard, rock-like scale which may reduce the flow in water pipes and slow down heat transfer in water heaters and boilers.

All natural water supplies contain at least some hardness, in amounts ranging from traces to several hundred grains per gallon.* In most areas the hardness concentration is between 3 and 50 grains per gallon, and in 85% of the United States, the local water supplies contain enough hardness to cause significant problems in home uses. The Water Quality Association classifies water supplies as follows:

Slightly Hard Water1-31/2 Grains per Gallon
Moderately Hard Water31/2-7 Grains per Gallon
Hard Water7-101/2 Grains per Gallon
Very Hard WaterOver 101/2 Grains per Gallon

When hard water is used in the home, it interferes with virtually every cleaning task, from bathing and personal grooming through dishwashing and laundering. Both soaps and synthetic detergents are affected by water hardness, which increases the amounts of cleaning agents needed, and produces poorer cleaning results.

When soaps are used in bathing and grooming, a film of sticky soap curd remains on the skin, and may hold particles of soil and bacteria, protecting them from removal. The soap curd interferes with the return of the skin to its normal slightly acid condition, and may lead to irritation and infection. Soap curd mon the hair makes it dull, lifeless and difficult to manage and arrange.

Even when synthetic detergents are used in dishwashing and laundering, hardness interferes. The active ingredient in the detergent mixture is partially inactivated by hardness, even though the product of the reaction stays dissolved. The alkaline "builders," added to the detergent mixture, to "cut" greases and oils, can react with these greases and oils to form soap, which in turn can produce soap curd when hardness is present in the water. Again, the deposits can protect soil and bacteria and interfere with thorough cleaning.

*The Grain per Gallon is a common basis for measuring hardness and certain other minerals in the United States. A grain weighs 1/7000th of a pound, and originally was based on the weight of a dry grain of wheat. A common aspirin tablet weighs about 7 grains, including binders. Thus one aspirin tablet dissolved in 1 gallon of pure water would produce a concentration per gallon.

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Hard Water Stains

Stained Water Glass

Hard Water Scale in Plumbing

Hard Water