In many plants such as chemical, textile, power, pulp and paper, water softening is required. In most of these installations, they have relatively low pressure boilers in the range of 100-150 psi where it is necessary to have a hardness content below 5 ppm and in many cases 1 ppm. It is necessary to remove the hardness; namely, the calcium and magnesium, in order to prevent the scale buildup within the piping system of these plants.

In this type of installation the resin is regenerated with sodium chloride and operated in the sodium form.

The following equation illustrates the softening process using strong acid cation exchange resin in sodium form:

2 R Na+1 Ca+2 R2 Ca+2 + 2 Na+1 2 R Na+1 Mg+2 R2 Mg+2 + 2 Na+1