What size water softener do I need?
Multiply your water’s hardness (grains per gallon) by the people in your home, the gallons each uses per day, and the days you want between regenerations. The answer is the grain capacity the softener must deliver.
Enter your numbers to see the size.
Example
10 grains per gallon × 4 people × 82 gallons (EPA’s average) = 3,280 grains a day. Regenerating every 7 days needs 22,960 grains, so the smallest common size that covers it is 24,000 grains. Common sizes: 24,000, 32,000, 40,000, 48,000, 64,000, 80,000 grains.
The nameplate size is the best case
A softener’s advertised grains are what it removes at its highest salt setting. At a lower, more efficient salt dose it removes less. These figures come from the makers’ own manuals:
| Model | Salt per regeneration | Grains removed |
|---|---|---|
| Morton Elite 34,000 Grain Water Softener | 2.7 lb | 13,700 |
| 8.6 lb | 29,200 | |
| 14.5 lb | 34,900 | |
| Whirlpool 40,000 Grain Water Softener System | 3.4 lb | 17,300 |
| 9.0 lb | 31,600 | |
| 15.5 lb | 40,000 | |
| Rheem PREFERRED Platinum 42,000 Grain WiFi Water Softener | 2.5 lb | 12,400 |
| 8.0 lb | 29,900 | |
| 16.3 lb | 42,400 |
So size for the capacity your model lists at the salt dose you plan to use, not the number on the box. Softener performance claims are certified under NSF/ANSI 44; each softener’s page here shows what the brand says and whether a listing we checked confirms it.
Don’t know your hardness?
Use the ZIP checker: for the systems where we have the utility’s report, it shows hardness and links straight back here with it filled in. Otherwise, your utility’s annual water quality report lists it.