How hard is the water in Belknap County, NH?
3.6 grains per gallon
Optional: a softener helps, but plenty of homes skip it.
The median hardness measured in Belknap County, NH is 62 mg/L as calcium carbonate, which is 3.6 gpg. That is moderately hard on the USGS scale. It comes from 64 samples at 61 sites between 1990 and 2021, drawn from groundwater wells, which is what most taps and private wells in the county draw on.
How much it varies here
Half the sites came in between 1.9 and 5.8 gpg. That spread crosses a decision line, so some homes here land on a different answer. A $10 test strip on your own tap settles it. Confidence in the county figure: high (how it is measured).
What to do next
At 3.6 gpg this is your call. Look for white film on glasses and crust on the shower head: if you see little of either, you can live without one. If you do want one, a 24,000-grain unit is enough, so ask for that size rather than a bigger one. Because Belknap County straddles a decision line, check your own tap with a $10 test strip before you spend anything.
More on when a softener is not worth it.
From 0.1 to 14.6 gpg
The softest single sample on record in Belknap County was 1 mg/L and the hardest 250 mg/L, a 250-fold gap. The top quarter of sites read above 5.8 gpg and the bottom quarter below 1.9 gpg.
Wells 3.6 gpg, rivers and lakes 0.7 gpg
64 groundwater samples from 61 wells put the median at 62 mg/L. 59 surface samples from 13 sites put it at 12.1 mg/L. In Belknap County the wells come out 2.9 gpg harder. Groundwater sits in contact with rock for years and picks up calcium and magnesium as it goes, so wells usually read harder. The two sources are close, so the county figure should hold whichever one your tap is on.
What a softener would cost to run
For a household of 3, a 24,000-grain unit covers a week between regenerations. Expect about 79 lb of salt a year (2 bags of 40 lb, about $14), and roughly 2,346 gallons of regeneration water. Installed, most units run $1,000 to $4,500; spread over 15 years with salt, that is about $114 a year.
Sizing at 3.6 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 216 | 24,000 | 26 lb |
| 2 | 432 | 24,000 | 53 lb |
| 4 | 864 | 24,000 | 105 lb |
| 6 | 1,296 | 24,000 | 158 lb |
Belknap County against the rest of New Hampshire
Among the 10 New Hampshire counties with data, Belknap County is number 5 of 10 counting from the hardest. Across the whole country it is harder than 25% of counties.
Softest in New Hampshire: Strafford County at 0.8 gpg. Hardest: Rockingham County at 6 gpg. Closest to Belknap County: Hillsborough County (3.6), Grafton County (3.7), Sullivan County (3.7).