How Water Softeners Work

Hard water contains calcium and magnesium ions. Water softeners use resin beads, which hold sodium ions. When hard water passes through the resin beads inside the softener, the beads attract the hard calcium and magnesium ions and give off soft sodium ions, this process is called Ion Exchange. After this process, the water leaving the softener is softened. Salt is put into a tank where water is added to make brine, which is used to wash across resin beads during the cleaning cycle (regeneration). The brine solution reverses the process and removes the hardness ions, which have built up on the resin beads, and replaces them with soft sodium ions. The system then rinses with fresh water to remove the brine. Some machines have an added back wash, this ensures the total removal of salt from the resin and also flushes out any debris that may have come in from the mains supply. Once again the system is ready to soften more water.

How a single cylinder softener works

singlecylinderwatersoftener_250x300Generally single cylinders water softeners use electricity to initiate and control the regeneration process. There are a few that require manual initiation of the regeneration process but few people want the hassle.

The water is directed into the inlet of the water softener, through the control valve and down the central distributor tube and into the bottom of the resin cylinder and passes up through the resin where the hardness ions are exchanged for the soft sodium ions, it then passes back into the properties water supply.

Each water softener has a certain capacity for the amount of softened water it can supply between regeneration dependent on the size (capacity of resin) and the hardness of the incoming mains water.

Timed controlled machine require the user to set the regeneration initiation process according to what they feel their water use is, this is normally worked out by consulting a chart which comes with the machine.

Meter controlled machines generally have a computer and a water meter incorporated into the control mechanism. The machine is set for the hardness of the water supply. The water meter monitors the water used and each night the computer calculates what the average use of water per day has been since the last time it regenerated, and then calculates whether there is enough capacity to last another day of typical water use. If it calculates that there is not enough capacity left to last another day, it will trigger a regeneration process that night. If it calculates you have more capacity left than has been used per day since the last regeneration it does nothing, it then does the calculation again the next night.

There are some meter/computer controlled machines that also have an added bonus that they do all the calculations as above. When the computer calculates that more than 50% of the capacity of the resin has been used it will trigger a regeneration that night, but to save any waste of salt it uses a proportional brining system. This means it will only use enough brine to regenerate the amount of resin capacity that has actually been used.  This can help overcome the problem of varying water use causing hard water to slip through when more water is used than the computer has calculated for.


Tkineticosoftenerdiagram250x250win cylinder water softeners are generally NON-electrically operated, using the pressure and flow of water to meter the water flow and operate the control of the water softener, only having to set the machines water meter according to the hardness of the incoming water supply. Every thing else is automatic, with NO adjustment necessary for varying water use, and NO interruption of the soft water supply as there is with a single cylinder system whilst it is regenerating.

Twin cylinder water softeners have the big advantage of not having to interrupt the supply of softened water to the property whilst regenerating. One way is to have one cylinder supplying softened water whilst the second cylinder is on standby. When the first cylinder is exhausted and unable to continue to soften water, the second cylinder takes over.  Then the first cylinder shuts down and goes through the regeneration process. The final part of regeneration is a backwash to ensure all salt and debris is removed from the resin.  When it is complete it waits on stand by until the cylinder in service is exhausted and the process reverses.

Type 2 (All other twin cylinder systems)

other_twin_cylindor_250x250Another way is for both cylinders to be in service together and after a predetermined use of water, one cylinder shuts down and goes through the regeneration process, whilst the other cylinder continue to supply softened water. When it has completed the regeneration process it goes back into service. Then after a further predetermined amount of water use the second cylinder shuts down and regenerates, and goes back into service when it has finished.

To try to reduce the amount of water used during regeneration, this type has removed the final part of regeneration (backwash) which is normally there to ensure the complete removal of any salt and debris from the resin before the regenerated cylinder is brought back into service.

Twin cylinder softeners are generally much smaller than single cylinder models due to not having to have enough capacity in the water softener to last until the early hours of the morning. However, they have a large daily capacity using less salt to produce the same amount of softened water. They use soft water to make brine and regenerate with soft water so not losing capacity, and the controls all work in softened water so no scaling problems in the machine, as can be found in single cylinder systems.