We call water "hard" if it contains a lot of calcium, magnesium or other minerals. All water softeners use resin to remove hardness and use salt to clean the resin when it gets full. Put hard water into the water softener system (with resin), through the carbonate-compound ion exchange resin, the water absorption of magnesium calcium release from the substitution of sodium ions, able to turn hard water into soft water to make it usable for various applications.

TRIWIN softener systems contain the salt bucket (sub-automatic or manual) used to backwash the resin to sustain softener for do effective and permanent use. The separate type water softener systems are known as the side-by-side model. These model water softeners have a separate brine tank (salt container) that uses common salt to create this brine solution. Since the brine tank can be disconnected from the resin tank, it is possible but potentially difficult to clean.