Ion exchange filters or water softeners
An ion exchange filter, commonly known as a water softener, is frequently used to eliminate iron and magnesium in water with high acid levels and where the metals are water-soluble (invincible to the naked eye).
Water softeners are also used for water hardness. Certain resins are built for a specific extraction. They will target a predetermined element like nitrates, arsenic or tannins. Salt recharges the ion exchange filter. The working principles are simple : the resin beads are saturated with sodium or chlorine who exchange a sodium ion with an iron, magnesium or calcium (hardness) ion.
When there is no more exchange capacity (resin beads are saturated with iron or other types of ions), the resin beads are recharged with highly concentrated salt water. It is strongly recommended that you do not completely soften the water because it will become aggressive and leave a bad taste. It could also leave some slime on your skin after you've taken a shower. To avoid these problems, water softeners are usually followed by a neutralizing filter to regain a calcocarbonic balance in the water