Softeners are for removal of water hardness.
Dissolved salts and water hardness
When rain water passes though the soil, it dissolves many salts.
Salts that contribute to hardness are salts of calcium, magnesium and iron.
When water has dissolved calcium and magnesium it is called hard water.
Iron salts also present problems of their own.
Iron salts can be removed from the water using a special iron filter.
Hardness is removed by a water softener.
Hard Water and Water Softeners
When hard water is heated, the dissolved calcium and magnesium salts form a scale in the heating container. This scale could be in a tea or coffee pot, in a pot of peas or soup, in a hot water pipeline or in your hot water service.
When hard water is used for bathing or washing clothes, the salts form a scum with the soap that coats the skin and hair, leaving it dull and drab.
It also leaves scum deposits on washed clothes.
This all results in a high soap bill.
The solution to all these problems is to soften the water.
What is a Water Softener?
A water softener basically consists of a tank containing softener resin.
The hard water enters the softener and passes through the resin bed where all of the hardness causing salts are exchanged with sodium salts.
The water then leaves the tank soft.
Softeners are rated by the amount of hardness salts they will remove before requiring to be re-activated (regenerated).
When this capacity is reached, the hardness material in the resin bed is washed down the drain, using a solution of common salt in water called brine.
This process of reactivating the resin is called regeneration.
The cost of salt in this process is relatively small, cents per kL.