This depends on several factors:
If space is at a premium then a block salt water softener is the smallest unit on the market - approximte H) 490mm- D)450mm - W) 215mm. These units can be installed under the kitchen sink, in the utility room, on a shelf in a cupboard or even outside in a frost proof cabinet. There is no electrical power supply needed and it will provide soft water for 1-10 people. When using a block salt water softener the salt consumption is approximately 1 block per person every 3 to 4 weeks and it may require frequent filling if there is a large number of people. It is suitable for High or Low pressure systems.
If space is not a problem and an electrical supply is available, then there are a number of suitable water softeners on the market. These units use tablet salt which is normally purchased in 10kg or 25kg bags. The units need to be sized correctly for the number of people in the house hold. A guide on salt consumption is approximately 1 x 25kg bag of salt for a family of 4 people per month.
We offer to visit your home free of charge, with no obligation to buy, to discuss with you which water softener would be best for your home. We would advise you on where the water softener could be installed and give a quotation.