A water softener works by ion exchange. Hard water flows through a tank of resin beads coated with sodium ions. The resin swaps out the calcium and magnesium minerals – which cause limescale – for a small amount of sodium. The result is soft water at every tap. Once the resin is saturated, the softener regenerates itself by rinsing through with brine from a separate salt tank. Most modern softeners need no electricity – they run entirely on your incoming water pressure.

Hard water enters your home via the mains water pipe. It flows to the water softener where it passes through a sealed cylinder filled with specially formulated resin beads.

This cylinder is where the process of softening occurs. 

The resin beads are coated with sodium ions. As the hard water passes through, the limescale is attracted to the sodium ions and changes places with it.

As the limescale clings to the resin, the now softened water exits the cylinder and flows through the water pipes in your home.

Eventually the resin beads become saturated with limescale and cannot attract any more. At this point the resin is cleaned or ‘regenerates’.

In addition to the cylinder of resin beads, a water softener will also have a brine tank. The brine tank holds the salt along with a predetermined amount of water.

When a water softener regenerates, salt solution from the brine tank passes through the resin to release the clinging limescale particles. The brine with the limescale is flushed out of the system, down your drain.

Your water softener is now ready to start softening the mains supply, hard water again.

This regeneration process slowly dissolves salt in the brine tank which will need to be replenished regularly. How often will depend on how much water your household uses.