How a water softener works

Ion exchange involves the use of a resin bed. Ion exchange resin is a very small synthetic bead-like material that looks a little bit like brown sugar. The beads are very small, about the size of a pin head.

The process is called Ion exchange because the ions calcium (Ca) and magnesium (Mg) are exchanged for small amounts of sodium (Na).

Hard Water

Here a drop of hard water containing magnesium (Mg) and calcium (Ca) approaches the resin.

The resin is coated with the sodium (Na) and is charged - ready to exchange.

As the drop of water passes through, the resin prefers magnesium (Mg) and calcium (Ca) to sodium (Na) so they swap.

The resin now has magnesium (Mg) and calcium (Ca)…

Soft Water

…and the soft water contains a small amount of sodium (Na).

This is what it looks like on a grander scale:

Service Cycle

• Hard water enters the resin bed…

  

• …and the hardness minerals are attracted to the resin.

  

  Softened water leaves the resin bed…

• …and 100’s of litres later,

  

  …softened water is still being produced, but…

• …it is now time to regenerate because otherwise…

  

  …hard water will break through into the house.

Regeneration cycle

• The brine picks up the minerals and they are flushed down the drain.

  

  Salt (brine) is now flushed through the resin in reverse.

• The last of the hardness minerals are still being flushed down the drain.

  

  A few litres later.

• Excess brine is flushed down the drain.

  

• Soft water is now used to rinse the resin.

  

  Regeneration completed and ready for service.

Water softeners use ion exchange (see above) and although they all differ in design they do share the following characteristics.

In this diagram note the brine tank containing salt, the pressure vessel containing resin and the control valve.

You will also see the inlet, outlet and drain. The overflow is not shown.

Service cycle (when it’s giving you softened water)

During the service cycle, hard water enters the control valve where it is sent down through the resin bed where the hardness minerals are removed.

The soft water then travels up through a tube and out to feed the house.

Regeneration cycle (when it’s cleaning itself)

The regeneration cycle will be initiated by the control valve. Salty water (brine) is sucked in by the control valve and up through the resin where it collects the hardness minerals and then flushes them out down the drain.