The first step is to ensure that you choose the size of water softener to match the number of people in the household Water Softeners Hub.
A water softener should ideally be sized based on the size of the property and the maximum potential number of occupants. This will ensure that there will always be soft water available and that the softener will not become exhausted before a regeneration is initiated.
Sizing a softener to the dwelling also allows for the softener to be a selling point should you move home and choose to leave the softener in situ. (a great many people become so used to soft water that if their new house does not have a softener they will fit the existing one in the new house). If you have a softener with too large a capacity for your circumastances, there is no problem whatsoever as it can be adjusted to suit your requirements.
The average person will use approximately 160 litres per day of water so by knowing the capacity of the softener it is possible to work out how many people it will cope with or size of dwelling and if it is sufficient. The usual minimum time between regenerations should be 2 days. In the UK a typical water hardness is 20 degrees Clarke, based on this a 10 litre softener would have a capacity of approx 1500 litres and therefore be suitable for a family of 4.
An 18 litre softener with a capacity of approx 2900 litres would therefore be adequate for up to 8 people or suit a 4 bedroom house.
When a domestic water softener reaches its capacity it has to go through a regeneration. In simple terms, this is where the resin is flushed through with a salt water solution and the hardness minerals (calcium, magnesium etc) is removed by the resin from the supply water by the sodium, the excess of which is also washed to drain at the latter end of the sequence. The time interval between successive softener regenerations is important to take into account.
A timer controlled valve is the least expensive option. The softener is programmed by the user to go through a regeneration at set intervals, i.e. on the second or third day, irrespective of the amount of water used. Timer control is best used when the number of residents and water usage is reasonably constant and the time between regenerations can be fairly accurately calculated.
The disadvantage to this is if the water usage increases sharply the resin may become exhausted and the water become hard or, if the house is left unattended, say for holidays, the unit will still regenerate at the pre set time unless re programmed. This will result in unnecessary over use of salt although it will not have any adverse affect on the softener itself.
The second option and most commonly preferred in the domestic market is a meter controlled valve. This type of unit has a preset capacity and reserve which will activate a regeneration when reached regardless of the time elapsed since the last one. These units are best when the water usage is variable or if there are prolonged periods of little or no use i.e. holiday home. A meter controlled softener offers more flexibility and can give the most cost effective use of salt.