How hard is the water in Hillsborough County, NH?
3.6 grains per gallon
Optional: a softener helps, but plenty of homes skip it.
The median hardness measured in Hillsborough County, NH is 61 mg/L as calcium carbonate, which is 3.6 gpg. That is moderately hard on the USGS scale. It comes from 42 samples at 30 sites between 1990 and 2022, 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 2.5 and 5.7 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 Hillsborough 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 0.8 to 13.4 gpg
The softest single sample on record in Hillsborough County was 14 mg/L and the hardest 230 mg/L, a 16-fold gap. The top quarter of sites read above 5.7 gpg and the bottom quarter below 2.5 gpg.
Wells 3.6 gpg, rivers and lakes 0.9 gpg
42 groundwater samples from 30 wells put the median at 61 mg/L. 505 surface samples from 101 sites put it at 15.2 mg/L. In Hillsborough County the wells come out 2.7 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 78 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 |
Hillsborough County against the rest of New Hampshire
Among the 10 New Hampshire counties with data, Hillsborough County is number 6 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 Hillsborough County: Belknap County (3.6), Coos County (3.4), Grafton County (3.7).