What is Hard Water?
Simply defined, when water is described as hard, it is because its dissolved mineral concentration is relatively high.

Water hardness is a characteristic representing the high concentration of minerals present in water. When this concentration is low, the water is described as soft. In other words, the harder the water, the more minerals are dissolved in it, the softer the water, the less minerals are present. Although there may be other types of minerals, it is usually calcium ions (Ca2+) and magnesium ions (Mg2+) that will be found in this type of water.


The categorization of water hardness is done according to its concentration in milligrams per liter of the listed minerals.


Table 1: Categories of water hardness

Soft water

Medium hard water

Very hard water

0 – 60 mg/L

61 – 120 mg/L

121 – 180 mg/L


Although the consumption of hard water is not harmful to human health since the human body needs minerals to function, hard water can cause problems to the equipment and shorten the life of the goods in contact with it.

One of the first complications that can be caused by the high presence of minerals in water is the appearance of carbonate deposits, better known as scale. Secondly, the high concentration of positive ions (Ca2+ and Mg2+) in water can have an impact on the effectiveness of certain products such as soaps and detergents.


What are the techniques to reduce water hardness?

As their name suggests, water softeners are very effective in reducing hardness, since they soften water by exchanging the ions present in it. The reason for this is that the softening principle works by exchanging ions in the system, hence the second name: ion exchange.


To summarize, the ionic exchange takes place in the tank of the softeners where there is a resin charged with weaker positive ions, such as sodium. When calcium and magnesium ions are in contact with sodium ions, they exchange places. Once the sodium is exhausted, the resin must be regenerated.


If you would like to learn more about water softeners and how they work, we suggest you visit this article.

What is Conductivity in Water?
Representing the ability of an aqueous solution to conduct an electric current, the conductivity of water is closely related to the concentration of total dissolved solids found in the water.