The Relation of Naturally Soft Water to Softened Water

It is unfortunate that softened water has been automatically classified as corrosive by some "experts." No doubt, this concept is the result of experiences with many of the water supplies in the New England states.

In the New England area much of the water is naturally relatively soft. This water also contains significant quantities of carbon dioxide. Thus, the water is both soft and corrosive.

The waters of the Southwest contrast sharply with those of the New England area in terms of hardness. Instead of being two to three grains hard, the waters of the Southwest range from 200 to 300 grains per gallon of hardness in some areas. At the same time, these waters are corrosive primarily because of their high mineral content which increases electrical conductivity.

These waters of the Southwest are corrosive primarily because of their high mineral content which increases electrical conductivity. In turn, this leads to acceleration of galvanic corrosion.

As can be seen from these two examples, hard water can be just as corrosive as soft water. Many people mistakenly believe that maintaining a certain amount of hardness in water is the best way to prevent corrosion. The idea is that hardness causes scale to form on pipe walls. This scale then serves to protect the plumbing system from the attacks of corrosion. While this method can work under certain conditions if carefully controlled, the method is not reliable in the home and is more apt to provoke problems than to lead to their control. Why? It would be difficult to establish and then maintain the right amount of scale coating. If too much were permitted to build up, it could restrict the rate of flow and hamper efficient heat transfer. Costs go up, efficiency goes down as scale forms. Thus, at best, hardness is a poor answer to corrosion.

Overall, softness is neither cause nor a cure for corrosion. And softening the water through the use of ion exchange equipment does not change the factors which affect corrosion: total minerals, electrical conductivity*, oxygen content, acidity, and temperature.

Read: Next