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Current IssueApril 20, 2014
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Ask The Expert: The long and short of softening
09/04/2002 
 
Question: Q: Could you please explain why water treated by a softener typically will show an increase in sodium, and a decrease in chlorides, when softener salt is composed of sodium chloride? Thank you.

Larry C. Aldridge
Hartville, Ohio
 

Answer: A: A "short" answer for you might be that, in the ion exchange process softeners/conditioners use, salt -- sodium chloride (NaCl) or potassium chloride (KCl) -- to regenerate the resins that remove contaminants from the water stream. This is done by ionic selectivity based upon the electronic charge or valence of the compounds being removed, which are "attracted to" or "regenerated off" of a resin bead. As the bead loads up with contaminants that are adsorbed or absorbed onto it, sodium or potassium is released from the bead in "exchange" for the undesirable element. Don't forget, this is in very small quantities. When the softener is regenerated, water from a brine tank containing pellets of salt -- NaCl or KCl -- is flowed through the resin bed and, because of the concentration, the undesirable contaminants are "backwashed" off of the resin in exchange for the Na or K part of the salt. The chlorides also are sent to waste in the backwash water. I believe that provides the simple answer to your question, even if it's not short. Keep in mind, the longer answer is more complicated and requires a broader understanding of water chemistry.

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