How hard is the water in Granite County, MT?
9.2 grains per gallon
A softener is worth it here.
The median hardness measured in Granite County, MT is 157 mg/L as calcium carbonate, which is 9.2 gpg. That is hard on the USGS scale. It comes from 25 samples at 9 sites between 1990 and 2026, 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 7 and 13.8 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: medium (how it is measured).
What to do next
At 9.2 gpg a softener is worth getting, mainly to protect the water heater and cut soap use. Get at least two quotes, ask each installer what grain capacity they are fitting, and check it against the sizing table below. Because Granite County straddles a decision line, check your own tap with a $10 test strip before you spend anything.
More on sizing a softener for your household.
From 6.5 to 14.7 gpg
The softest single sample on record in Granite County was 111 mg/L and the hardest 251 mg/L, a 2-fold gap. The top quarter of sites read above 13.8 gpg and the bottom quarter below 7 gpg.
Wells 9.2 gpg, rivers and lakes 2.6 gpg
25 groundwater samples from 9 wells put the median at 157 mg/L. 827 surface samples from 144 sites put it at 43.8 mg/L. In Granite County the wells come out 6.6 gpg harder. Groundwater sits in contact with rock for years and picks up calcium and magnesium as it goes, so wells usually read harder. A utility here that draws from the river can deliver noticeably different water from a private well next door.
What a softener would cost to run
For a household of 3, a 24,000-grain unit covers a week between regenerations. Expect about 200 lb of salt a year (6 bags of 40 lb, about $36), 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 $136 a year.
Sizing at 9.2 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 552 | 24,000 | 67 lb |
| 2 | 1,104 | 24,000 | 134 lb |
| 4 | 2,208 | 24,000 | 269 lb |
| 6 | 3,312 | 24,000 | 403 lb |
Granite County against the rest of Montana
Among the 56 Montana counties with data, Granite County is number 43 of 56 counting from the hardest. Across the whole country it is harder than 48% of counties.
Softest in Montana: Lincoln County at 3.4 gpg. Hardest: Rosebud County at 138.9 gpg. Closest to Granite County: Deer Lodge County (8.9), Hill County (8.7), Lewis and Clark County (9.8).