The short answer
At 15 gpg, two people need about 15,750 grains a week, so a softener rated about 24,000 grains covers them at an efficient setting.
By hardness
| Hardness | Grains a week | Rating to look for |
|---|---|---|
| 10 gpg | 10,500 | about 14,000 |
| 15 gpg | 15,750 | about 21,000 |
| 20 gpg | 21,000 | about 28,000 |
| 25 gpg | 26,250 | about 35,000 |
Don't go too small
Portable units suit RVs, not homes; a small whole-house unit still needs enough flow for a shower and an appliance at once.
Units that fit
Tier1 WS-165-132 32,000-Grain Water Softener, Kenmore 350 32,000-Grain Water Softener, NPGLOBAL NPG-124 16,000-Grain Portable Water Softener. See the small-home shortlist.
Products mentioned
Questions readers ask
What size water softener for two people?
About 21,000 to 28,000 grains rated at 15 to 20 gpg.
Is a 32,000-grain softener too big for two people?
It runs longer between regenerations; on a metered valve that's fine.