What is Water Softening Resin?
During the softening process, water is passed through a column of ion exchange resin. The calcium and magnesium ions present in the water are exchanged on the resin beads for an equivalent amount of sodium ion. The softened water exiting the Water Softener is significantly higher in sodium than the raw water. This basically is “The Ion Exchange Process”.
The exchange of hardness for sodium is not perfect or complete. A small amount of ‘hardness’ usually passes through the softener in the treated water. However, testing of the softened water discharging from a properly operating softener unit for hardness at this stage will usually not detect the trace amount of hardness.
Eventually, more and more hardness will escape in the water and can be detected using a normal hardness test kit. At some stage, it will be necessary to rejuvenate or regenerate the resin so that the quality of the softened water can be maintained at the required standard.
Regeneration of the resin is achieved by passing a solution of salt (Brine or Sodium Chloride) through the resin to displace the calcium and magnesium ions that have been taken up by the resin beads from the water. The sodium from the brine replaces the calcium and magnesium ions on the resin. When this process is complete, the resin can be used again for softening water.
Generally, the more efficiently the brine is used, the more efficiently the hardness is displaced from the resin. For more demanding applications such as softening boiler water, more brine needs to be used. This is to minimise the amount of resin that is left on the resin when the softener is brought back into service. If insufficient brine is used, hardness leakage from the softener will be higher.