How Whole-Home Water Softeners Work

If you live in an area with hard water, you may have been told that you need a water softener. You may wonder, “Isn’t a water softener just a glorified filter?” No, a water softener is quite a bit more complex. A basic understanding of how a water softener works can help you decide if a whole-home water softener is a good investment.
First, instead of thinking of a water softener as a filtering system, think of it as a water conditioning system. Water softeners are ion exchangers that remove positively charged ions, primarily calcium and magnesium. Because of this, they are not typically effective at removing many other impurities in water (and many of those impurities are not considered hard water minerals).
While there are variations in the exact way manufacturers build their water softeners, they all share the same basic components.
  • A mineral tank
  • A brine tank
  • A control system
  • A drain

Mineral tank. Hard water from your home flows into the mineral tank. This tank contains beads that have negatively charged sodium or potassium ions. The positively charged ions that make water hard are drawn to the beads and cling to them. When this happens, the negatively charged sodium/potassium ions are released. This exchange is how sodium is added to the water and why some people opt to use potassium instead.

Brine tank. Of course, at some point the negatively charged sodium ions become depleted and completely replaced by the positively charged ones from the hard water. This is where the brine tank becomes important.
Brine is simply a salt-water solution, although some people use potassium instead of salt. The solution is highly concentrated. When the negatively charged ions in the mineral tank become depleted, they are replaced through a process called regeneration. The strong brine is flushed into the mineral tank. This causes another ion exchange, except now the positively charged hard water ions are replaced with the negatively charged sodium ions.

WarningIf you buy a water softener online, be sure to check local regulations. Some areas forbid the use of sodium-based water softeners because of their potential impact on the environment. Their use is also discouraged for people on septic systems.

Drain. Regeneration results in waste water which is disposed of via the drain.

Control System. As the name suggests, this component manages the water softening process. The most common control systems are automatic—and for good reason. Once set-up, they require almost no attention from the owner, save for replacing the salt/potassium. If you are unable to connect your water softener to a drain, you will have to manually drain the tank and discard the waste water.