Soft Water Salt — Frequently Asked Questions

No, and this is commonly misunderstood. Softening is done by a bed of ion exchange resin carrying sodium ions, which swaps them for calcium and magnesium in the incoming water. The salt's only job is to regenerate that resin: a concentrated brine flushed through the bed strips the accumulated hardness ions off and restores the sodium, and the hardness goes to drain.

Because of insoluble matter and additives. Rock salt carries grit and clay that block the injector and foul the resin bed, and de-icing salt contains anticaking agents that are equally damaging. Water softener salt is refined to high purity with low insolubles specifically so it will not degrade the resin, which is expensive to replace.

Physical form rather than chemistry. Tablets are compressed and dissolve evenly, which suits most domestic and commercial units. Blocks are used in specific machine designs. Granules dissolve faster and suit high-consumption commercial installations. The choice is dictated by the softener design, and the manufacturer's specified form should be used.

It contains sodium in proportion to the hardness removed, since the exchange swaps two sodium ions for each calcium or magnesium ion. For most supplies the added sodium is modest, but for very hard water, or where a low-sodium diet is a concern, a separate unsoftened drinking tap is the usual arrangement.