How hard is the water in Flathead County, MT?
11 grains per gallon
A softener will pay its way here.
The median hardness measured in Flathead County, MT is 189 mg/L as calcium carbonate, which is 11 gpg. That is very hard on the USGS scale. It comes from 5 samples at 5 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 10.9 and 12 gpg. The whole middle of that range gives the same answer, so a test of your own tap is unlikely to change it. Confidence in the county figure: medium (how it is measured).
What to do next
At 11 gpg a softener pays its way here. Before you buy, check the quoted unit's grain capacity against the sizing table below, and ask whether it regenerates on demand, which uses less salt than a timer. Call your utility for its own report if you are on city water.
More on sizing a softener for your household.
From 9.9 to 22.7 gpg
The softest single sample on record in Flathead County was 169 mg/L and the hardest 388 mg/L, a 2-fold gap. The top quarter of sites read above 12 gpg and the bottom quarter below 10.9 gpg.
Wells 11 gpg, rivers and lakes 5.4 gpg
5 groundwater samples from 5 wells put the median at 189 mg/L. 956 surface samples from 169 sites put it at 92.3 mg/L. In Flathead County the wells come out 5.6 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 241 lb of salt a year (7 bags of 40 lb, about $43), 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 $143 a year.
Sizing at 11 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 660 | 24,000 | 80 lb |
| 2 | 1,320 | 24,000 | 161 lb |
| 4 | 2,640 | 24,000 | 321 lb |
| 6 | 3,960 | 32,000 | 482 lb |
Flathead County against the rest of Montana
Among the 56 Montana counties with data, Flathead County is number 40 of 56 counting from the hardest. Across the whole country it is harder than 55% of counties.
Softest in Montana: Lincoln County at 3.4 gpg. Hardest: Rosebud County at 138.9 gpg. Closest to Flathead County: Madison County (10.7), Chouteau County (11.4), Gallatin County (11.4).