The gas heaters operated and tested on hard water consumed 29.57% more Btu's of energy than the gas heaters operated and tested on softened water for the same amount of energy delivered.
The electric heaters operated and tested on hard water consumed 21.68% more Btu's of energy than the electric water heaters operated and tested on softened water for the same amount of energy delivered.
It is not necessary to heat water to a high temperature to produce scale. Any increase above the original temperature of the water can cause lime scaling to occur.
Although no chemical reaction occurs which causes calcium sulfate to deposit when the water is heated, this hardness mineral is unusual as it is less soluble in hot water than in cold.
Hard water can also be troublesome in industry. In many industrial applications, however, not only must hardness be removed from the water, but all mineral content must be eliminated. Mineral deposits can cause serious difficulties in boilers, air conditioning systems, gasoline and diesel engine cooling systems.
Water is an excellent solvent. Our previous articles outlines how water collects the various contaminants found in it.
As moisture falls through the atmosphere, it absorbs amounts of carbon dioxide (CO2).It also collects amounts of this gas on and in the ground from decaying vegetation. Since carbon dioxide is a product of both combustion and decay it is present in practically all water supplies.
When carbon dioxide dissolves in water, some of it forms a weak acid called carbonic acid.
H20 + C02 --> H2C03
This acid is responsible for dissolving limestone or carbonate deposits in the earth. It also produces certain types of corrosion in water and steam lines. The natural solvent action of water is enhanced by carbonic acid making it even more effective in dissolving hardness minerals.
Hardness minerals-calcium and magnesium are in plentiful supply. While they are not found in their elemental form in the earth, they occur in combination with other elements in an abundance of forms. Common calcium minerals include chalk, limestone and marble. These substances are chiefly calcium carbonate (CaC03) or mixtures of calcium and magnesium carbonates and other impurities. Gypsum is calcium sulfate (CaSO4). In this compound calcium is combined with sulfur and oxygen.
Epsom salt is magnesium sulfate (MgS04).
Ions of the following calcium and magnesium compounds are found in water:
The amounts of these various chemical compounds present in water supplies depend on two factors:
1. The minerals present in the earth; and
2. Their solubility in water related to carbon dioxide (CO2) concentration.
On a decreasing scale of solubility, calcium chloride, magnesium chloride and magnesium sulfate are extremely soluble. They may be found in water in almost unlimited amounts. Calcium sulfate is less soluble. At the other end of the solubility scale are the calcium and magnesium carbonates which are very slightly soluble in pure water. The amounts of these last two compounds in water rarely exceeds two and five grains respectively. Calcium and magnesium carbonates are seldom found in natural water supplies because of their very low solubility.
While "insoluble" carbonates are rarely found, they are found in their extremely soluble form in hard water as calcium and magnesium bicarbonates. When water containing carbon dioxide comes into contact with calcium and magnesium carbonates in the ground, a chemical reaction takes place. The "insoluble" carbonate forms of magnesium and calcium are transformed into highly soluble bicarbonates. These are the principal hardness compounds found in water. It is interesting to note that these bicarbonate forms exist only in solution. If heat is applied to water, the bicarbonates can release carbon dioxide and revert to their carbonate or "insoluble" state. For this reason, bicarbonate hardness is often referred to as temporary hardness.
Hardness caused by the presence of the soluble chlorides and sulfates of calcium and magnesium are classified as "permanent" because these compounds cannot be removed from water through simple heating.
When these chemical compounds are dissolved in water, their ions are released
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