Guides / Water · Updated
Water softener capacity chart
Capacities from Pentair's whole-house softener manual; use from EPA's 82 gallons a person a day. Checked November 2026.
Short answer
A family of four on 15 grain water uses about 4,900 grains a day. A 1.5 cu ft softener holds about 37,000 grains at a middle salt setting, so it regenerates roughly once a week. Lower salt settings are more efficient but hold fewer grains.
Capacity by size and salt
| Resin | Low salt | Medium salt | High salt |
|---|---|---|---|
| 1 cu ft | 16,660 grains at 3.9 lb | 24,593 grains at 7.9 lb | 30,726 grains at 15.8 lb |
| 1.5 cu ft | 24,990 grains at 5.8 lb | 36,889 grains at 11.8 lb | 46,089 grains at 23.7 lb |
| 2 cu ft | 33,332 grains at 7.8 lb | 49,186 grains at 15.8 lb | 61,452 grains at 31.6 lb |
Grains a day by household
| People | 5 gpg | 10 gpg | 15 gpg | 20 gpg | 25 gpg |
|---|---|---|---|---|---|
| 1 | 410 | 820 | 1,230 | 1,640 | 2,050 |
| 2 | 820 | 1,640 | 2,460 | 3,280 | 4,100 |
| 3 | 1,230 | 2,460 | 3,690 | 4,920 | 6,150 |
| 4 | 1,640 | 3,280 | 4,920 | 6,560 | 8,200 |
| 5 | 2,050 | 4,100 | 6,150 | 8,200 | 10,250 |
| 6 | 2,460 | 4,920 | 7,380 | 9,840 | 12,300 |
People × 82 gallons × grains per gallon. Hardness in mg/L (ppm)? Divide by 17.1. Add 5 grains for every mg/L of iron (GE, Pentair). Divide the softener's capacity by your daily grains to see how many days it goes between regenerations; the softener size calculator does it all and picks the size.
Sources: Pentair whole-house softener manual, EPA WaterSense statistics, GE softener manual.