This chart will help you to choose a water softener size that is right for your needs. You will need to know the number of people in your household and the grains of hardness per gallon in your water. If you need a quick and easy hardness testing kit, go to our Water Test Kit page.

Hardness in Grains per Gallon

Number of People in Family +1*

	1	2	3	4	5	6	7	8
0-10	24,000	24,000	24,000	32,000	32,000	32,000	40,000	40,000
11-20	24,000	24,000	32,000	32,000	40,000	40,000	40,000	48,000
21-30	32,000	32,000	40,000	40,000	48,000	48,000	48,000	64,000
31-40	40,000	40,000	48,000	48,000	48,000	64,000	64,000	80,000
41-50	64,000	64,000	80,000	80,000	80,000	96,000	96,000	110,000
51-75	64,000	80,000	80,000	96,000	96,000	110,000	110,000	110,000
76-100	80,000	80,000	96,000	96,000	110,000	110,000	110,000	110,000

This reference guide is based on every 4th night regeneration.

*Additional person compensates for water using appliances.

Formula for sizing softeners

Capacity = No. of People x Hardness x 70 Gallons x Days Between Regeneration

Ex: A family has 4 people with 33 grains per gallon hardness with no iron.

4 + 1(for appliances) x 33 Grains/Gal. x 70 Gallons x 4 Days = 46,200 Grains. In this example, 46,200 grains of capacity is needed on average every 4 days. Because no iron is present, the low salt setting can be used. Select the softener that will provide more than 46,200 grains at the low salt setting.

A water softener will remove clear water iron (iron in solution). When removing iron with a softener, compensate the hardness by a factor of 5 grains per gallon for every part per million of iron.

 

Ex: A family has 3 people with 22 grains per gallon hardness and 3 parts per million iron.

3 + 1(for appliances) x 37 Grains/Gal. x 70 Gallons x 2 Days = 20,720 Grains. In this example, 20,720 grains of capacity is needed on average every 2 days. With iron present, the softener should regenerate every other night and use the medium salt setting. Select the softener that will provide more than 21,000 grains at the medium salt setting