Ion exchange water softening. How do I find out if the installation functions properly?

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Ion exchange water softening. How do I find out if the installation functions properly?

If you have a water softener at home or you have to work with Na-softener, and it is not possible to make a chemical analysis for hardness, then there is an easy way to find out whether the softener installation functions properly.

To do this, it is necessary to measure the electrical conductivity of the source and softened water during the operation of the softening unit. In the vast majority of cases for fresh water, the value of the electrical conductivity of softened water will always be greater than the value of the source water .

A bit of theory.

During the process of ion exchange water softening, the multivalent ions contained in the source water are replaced by the monovalent sodium ion contained on the ion exchange resin. Multivalent ions of the source water are the hardness ions (calcium and magnesium).

Thus, the number of ions in water does not change, but their type changes. In this case, one sodium ion can transfer more electric charge than one calcium or magnesium ion in the presence of sulfates. Accordingly, softened water almost always has a higher electrical conductivity than the original non-softened water.  Only if there are no sulfate ions in the water (which is practically impossible for natural water), the softened water will have a lower electrical conductivity than the source water.

The approximate sequence of actions for measuring the electrical conductivity of water should be as follows:

full version - https://tiwater.info/en/ion-exchange-water-softening-how-do-i-find-out-if-the-installation-functions-properly/

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8 Comments

  1. Great discussion. Can anyone provide data on Langelier Indices before and after softening? What should the desired hardness value be after softening?

    1 Comment reply

    1. It all depends on the composition of the source water and where the softened water will be used. it is necessary to consider each specific moment.

  2. Very interesting.  The national power utility companies in India, impose a Na based conductivity measurement as intermediate quality parameter in resin base plants or outlet of acid cation exchanger.  Precisely they want to know role of Na slippage and conductivity that it contributes.  Interesting read, Ivan! 

    1 Comment reply

    1. Control of acid cation exchanger  by electrical conductivity is a very interesting topic. I will present my thoughts on this a little later.

  3. The best method I am aware of for determining if water is soft

  4. Thank you for your comments. I also used to think that if the salt content of the source and softened water does not change, then the electrical conductivity does not change either. But it turned out that the electrical conductivity of softened water increases. And the more sulfate in the water, the greater the difference in the value of electrical conductivity is.

    More detail - https://tiwater.info/en/the-method-of-controlling-the-process-of-ion-exchange-water-softening/

    This method is not a direct alternative to the colorimetric method. This is just a variant of operational continuous monitoring. Monitoring can be remote.

    When the water is fully softened, the Langelier index will be negative. The water will be corrosive. If water is used for water supply, it is necessary to make a mixture of softened and source water.

  5. Very interesting discussion. The purpose obviously is to exchange calcium and magnesium ion for sodium ions. What happens to the Langelier Index? And what is the ideal hardness value after softening?

  7. Effectively conductivity is often SLIGHTLY higher in the softened water than in the feed Na+ ions are more mobile than the other ions), but it depends also in the temperature.

    So the best way to know if the softener works well is to measure the hardness with a colorimetric method (very fast and not expensive).

  8. I am sorry to disagree, but a Base-exchange softened water should have the same conductivity as the water feeding it.  If the conductivity is higher, then the usual cause is salt, which is used to regenerate the resin, is present in the water and indicates over-brining or poor backwash.  There are simple tests for hardness where a volume of water is poured into a plastic container and a tablet is dropped into the water.  A lid is put on and shaken.  If the water is blue or green the unit is providing soft water while if it is red it is failing to provide soft water.