I've read that there are single units and conditioners with reservoirs. I've gathered that they both need to be replenished with conditioning salt. I have a two piece (below) unit and am wondering how exactly it works and what kind of maintenance I am supposed to perform on it.

When I looked in the reservoir, there's only a small amount of water and it doesn't look like there's any salt:

From online research, it seems as though I have a unit that refills daily which is wasteful. I recently saw a single unit from Costco and am curious whether this would be better than what I currently have.


1 Answer 1


The reservoir of your unit needs to have a reasonable amount of rock salt in it in order to create a brine. You can fill it with salt, then check it occsionally and refill when you can see water over the remaining salt.

The Costco unit you linked still has two tanks, they are simply contained in a single package. Ion exchange water softeners all work on the same principal. Other methods of softening include chemical treatment, reverse osmosis, and distillation. Hard water is caused by dissolved minerals, mostly potassium and magnesium, in the water. These minerals can precipitate out and cause deposits of scale, as well as prevent proper functioning of soap chemistry.

Water can be softened by exchanging the undesirable mineral ions with sodium ions which do not precipitate and do not interfere with soap chemistry. This is achieved by passing water over resin beads that have been soaked with a brine solution such that they are saturated with sodium ions. Because of the way the resin is chemically charged, water would rather have sodium ions and the resin would rather have potassium and magnesium ions, so an exchange occurs and the water is softened.

Eventually, the resin's supply of sodium ions is depleted and must be recharged. This is done by exposing the resin to a concentrated sodium brine. The high concentration forces out the accumulated magnesium and potassium ions and replaces them with sodium ions. The recharge water, containing unabsorbed sodium, as well as potassium and magnesium ions is then flushed away.

It is unfortunate if your unit recharges once a day no matter what. Most softeners have more flexible methods of determining when to recharge, either by time passed or amount of water used. Measuring water used directly addresses the important variable, but timers generally work well once you determine the typical water usage of your family.

Ion exchange softeners are pretty much maintenance free other than replenishing the salt supply. The manufacturer of the softener in my home suggests adding a half cup of household bleach to the brine every time the salt is replenished to keep any potential growths of algae or bacteria from gaining a foothold as the only other maintenance item.

  • Are there different types of salts, or do I need a particular kind depending on the reservoir?
    – Kermit
    Jun 21, 2013 at 20:57
  • I have something like this in my home. It has buttons to program it when to use the salt to do the recharges. At first the one that installed it set it for once every day and it ate up a lot of salt. After some trial and error we found that for a 3-person usage of water a weekly program is enough. Unless it uses very small amounts of salts or use a lot of water at your home the daily recharging seems wasteful. 25kg of salt lasts about 2 to 2 and a half months. My unit is a Lamborghini. lamborghinicalor.az/content.php?page=11&lang=en&cid=18
    – vlad b.
    Jun 21, 2013 at 20:57
  • 2
    @FreshPrinceOfSO - You want sodium chloride salt. All salt packaged for softener use is sodium chloride. There may be various physical configurations, granules, pellets, in various sizes. There may be additives to inhibit rust or something, or not. Since the goal is for the salt to dissolve into a concentrated brine solution, the variants don't make a huge difference. Larger particles may last longer in the tank. As long as it's packaged for softener use, it will work. There are other salts for other uses besides water softening.
    – bcworkz
    Jun 22, 2013 at 18:39
  • 1
    I think you have potassium confused with calcium here.
    – Ecnerwal
    Jun 6, 2016 at 12:49

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