20 March 2017

How big of a water softener do I need?

Household water softeners are rated by the number of grains of hardness they can remove through a specific volume of resin in the tank, and the amount of salt needed to regenerate the resin.

There are 2 questions you need to answer about your household before you know which water softener to buy or rent. 1) The hardness of your water 2) The expected demand of soft water in the household. 

Your city will know your water hardness or you can use water hardness test strips to determine.  As for your water demand/consumption, you can use your water bill to determine your average usage. Simply divide your water bill’s water consumption number by the number of billing days for that billing period. This will give you your household’s average daily water use.

Then, just multiply the hardness of the water by the number of people in the household by the gallons of soft water used per day.  For example, let’s assume a household of 4 each using 80 gallons of water per day, and a water hardness of 12 gpg.  4x80x12 = 3840 grains per day of hardness that must be removed.  Ideally a water softener should regenerate about once per week, so one would choose a softener size that would be closest to regenerating once per week with the given soft water demand (typical sizes are 24K, 32K, 40K, 48K, 64K).  So for this example, a 24K softener would need to regenerate every 6.25 days and a 32K softener would need to regenerate every 8.3 days – either of those sizes would be in the right ballpark, but one would not want to go bigger or smaller.