Softeners come in various sizes, and are rated by the amount of grains of hardness it can handle before moving with regeneration. If the unit handles around 12,000 to 16,000 grains, it's said to be small. Whereas if a unit handles around 20,000 to 40,000 grains, its considered to be medium and anything above 40,000 is considered to be large.
There is an easy way to indentify which softener would be appropriate for your family by multiplying each family member with 75. For example, if you have five members at home, you can multiply this figure with 75 which is the average no. of gallons used per person everyday. Like that we get an answer 375 gallons which is then multiplied with the no. of gallons of hard water material present, say 10. You now get your figure of 3750 which is the amount of hard water material you need to remove per day. Once you know what you want, you can easily compare to the recharge cycle and can find out the size of the softener need to satisfy such a family size. The whole idea behind this calculation is to get a unit that would best fit your requirements and stays in the budget. You should buy a kind of unit that would at-least run for over 3 days before recharge in normal home without any visitors.
Water Softener Controls
There are questions which can tickle the mind as what controls the regeneration process and how long does it takes and how much salt and water is required for recharging etc. There are even fully-automatic types of units which get recharged with occasional salt re-filling. In automatic units there are many ways but only two very commonly used.
there are electronic timers or clocks which will trigger the auto recharge depending upon present day, time and your average usage. If on one particular day, you have an unusual excess usage then this type of unit might not be able to assist much. Sodium will be wasted along with water whether they regenerate or not, but will continue to recharge.
There is a more sophisticated way known as demand-initiated regeneration (DIR) which senses when the resin needs to be recharged with the help of either a meter or electronically to calculate the usage. A DIR not only saves on sodium (Salt) and regenerations due to the fact that it doesn't recharge unnecessary. In addition, it works absolutely fine during those time when you have visitors at home.