The short answer
Very hard water needs more capacity per person; size from your test and expect more frequent regeneration and salt use.
Sizing at 25 gpg
| People | Grains a week | Rating to look for |
|---|---|---|
| 2 | 26,250 | about 35,000 |
| 3 | 39,375 | about 53,000 |
| 4 | 52,500 | about 70,000 |
| 5 | 65,625 | about 88,000 |
Salt use
More hardness means more salt: estimate it with the salt calculator.
Well water
Penn State recommends softeners for iron removal only when hardness is between 3 and 20 gpg; above that, test for iron and treat it separately. High-capacity units: AFWFilters Fleck 5600SXT 64,000-Grain Water Softener and Filter System, AFWFilters Fleck 9100SXT 64,000-Grain Water Softener and Filter System.
Products mentioned
Questions readers ask
What size softener for 25 gpg water?
About 13,000 grains a week per person; four people need a unit rated about 70,000 grains.
Is there a limit to the hardness a softener can handle?
Makers state limits for their units; check the listing and size up for very hard water.