How do water softener systems work? Are they magic? Adding salt gets rid of other minerals. . . HOW? I’ve never understood this. I’m 54, male.
In: Chemistry
They use a principle called ion exchange. They have big filter cartridges filled with plastic beads. However, the beads are made from a special type of plastic, which has negative charges on its surface. Positively charged ions – such as sodium, calcium, magnesium and so on, are attracted to the negative charges on the beads and get stuck.
Calcium and magnesium, which cause water “hardness” are more strongly positively charged than sodium, so if there is a choice, the calcium and magnesium will stick to the beads in preference to the sodium, and will push the sodium off into the water.
The first step in the process is to load the beads with sodium. This is done by taking a concentrated salt solution, and running it through the cartridge. There is so much sodium in the brine, that it pushes any calcium or magnesium off the beads. After about a 30 minute soaking time, the waste brine then goes down the drain, carrying the calcium/magnesium with it.
The cartridge then gets rinsed out with fresh water, and then gets switched in line with the water supply. As water flows past the beads, the calcium/magnesium in the water preferentially stick to the beads, and the sodium is released.
At some point, all the sodium on the beads is depleted and the beads are saturated with calcium/magnesium, and the system needs to be regenerated again – so the system mixes up a salt solution and sends it through the beads, and the process repeats. Most water softeners have a water meter or timer, which triggers regeneration – the trigger needs to be adjusted for how much calcium is in the water (and in the case of a timer system, how much water is used on a daily basis).
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