How hard is the water in Coos County, NH?
3.4 grains per gallon
You do not need a softener here.
The median hardness measured in Coos County, NH is 58 mg/L as calcium carbonate, which is 3.4 gpg. That is soft on the USGS scale. It comes from 84 samples at 79 sites between 1990 and 2024, 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 2.1 and 5.6 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
You can skip the softener. At 3.4 gpg the most a softener would fix is the odd water spot. If a salesperson in Coos County says otherwise, ask to see their reading in grains per gallon and compare it with this one. Because Coos 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 0.4 to 49.7 gpg
The softest single sample on record in Coos County was 7 mg/L and the hardest 850 mg/L, a 121-fold gap. The top quarter of sites read above 5.6 gpg and the bottom quarter below 2.1 gpg. So even in a soft county, a handful of wells here produce water hard enough to scale a heater.
Wells 3.4 gpg, rivers and lakes 0.7 gpg
84 groundwater samples from 79 wells put the median at 58 mg/L. 380 surface samples from 68 sites put it at 12.3 mg/L. In Coos 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.
Coos County against the rest of New Hampshire
Among the 10 New Hampshire counties with data, Coos County is number 7 of 10 counting from the hardest. Across the whole country it is harder than 24% of counties.
Softest in New Hampshire: Strafford County at 0.8 gpg. Hardest: Rockingham County at 6 gpg. Closest to Coos County: Hillsborough County (3.6), Belknap County (3.6), Merrimack County (3.1).