How to calculate water softener size?

Our 32,000 grain unit (1 cubic foot of resin) is more than enough capacity for the majority of homes. Conditions that would necessitate a larger unit include: a larger family (6 or more), a larger house (4000sq ft.+), and/or very hard water (over 15 grains).

A water softener should ideally be sized so that it does not regenerate more than every three days (wasting water and salt) and does not go more than 14 days without being regenerated (can cause compacting of resin, and fouling with sediment or iron). It's probably best to wait 7 days between regenerations, especially if iron is present. Our 32,000 grain unit (1 cubic foot of resin) is more than enough capacity for the majority of homes. There are some circumstances that would necessitate the purchase of a larger unit, such as a larger family (6 or more) and/or very hard water (over 15 grains).

It is possible to programme the computer-control valve for more efficient salt use by setting the capacity to a lower amount. A one cubic foot softener, for example, has a peak capacity of 32,000 grains at a salt setting of 18.5 pounds per regeneration. This yields 1729 softening grains per pound of salt (32,000/18.5).

You can programme it for a capacity of 24,000 grains and a salt setting of 8.5 lbs. This would yield 2823 grains per pound of salt, nearly doubling the efficiency. Granted, it will regenerate slightly more frequently, but since it only uses about Rs. 10 of water per regeneration, this isn't a big deal. Having said that, the capacity options listed below list both the peak and efficient levels to help you make a better decision.

-1.0 cubic foot of resin with a grain peak of 32,000 and an efficiency of 24,000

-1.5 cubic feet of resin - peak grain count of 48,000, efficiency of 32,000

-2.0 cubic feet of resin - peak grain count of 64,000, efficiency of 40,000