what’s the function of salt in a water softener?
Hard water contains CaCO[sub]3[/sub]. This salt has an odd solubility curve, and forms hard insoluble deposits in pipes and on heating elements, as well as interfering with detergents and soaps. So it is considered a bad thing. So the trick is to improve the solubility of the salts present in the water. The easiest approach is to replace the Ca[sup]2+[/sup] ions in the water with 2Na[sup]+[/sup] - Na[sub]2[/sub]CO[sub]3[/sub] has no solubility issues, and does not impact detergents. KCl (potassium chloride) can also be used instead of NaCl, but I guess that the column ions are different.
So a water softener has an ion exchange column. This contains resin beads with lots of [sup]2+[/sup] binding sites, tuned via chemistry to have a good affinity for Ca[sup]2+[/sup] ions, but which will allow 2Na[sup]+[/sup] ions to fit in.
At the start, the ion column is loaded with Na[sup]+[/sup]. Hard water is passed through the column, and the Ca[sup]2+[/sup] ions replace the Na[sup]+[/sup] ions in solution, and the water is softened. Eventually the ion exchange column is exhausted, so a backflush process is run, with brine (saturated NaCl). This forces the Ca[sup]2+[/sup] ions out of the column due to the concentration differences, and reloads it with Na[sup]+[/sup] ions. CaCl[sub]2[/sub] and excess NaCl is flushed out the system and down the drain.
Si
That pretty much explains it. If those of you reading don’t follow the chemistry there, simply put the resin bed will chemically draw whatever is more prevalent among certain elements and release the less prevalent one. A water softener can be recharged with sodium chloride potassium chloride or hydrogen.
I would be interested in potassium salts that are sold for water softeners; where might I find them? One drawback of sodium-charged water softeners is a slight increase in the sodium content of your water which is not good for people with high blood pressure. If I could find a potassium salt based product, I would use it.
I’ve seen it nearly everywhere that sells softener salt. Grocery stores, softener stores, and a store that sells only salt.
We just have a tap that runs filtered unsoftened water in the kitchen. Saves hassle.
Si