How hard is the water in Missoula County, MT?
8.4 grains per gallon
A softener is worth it here.
The median hardness measured in Missoula County, MT is 145 mg/L as calcium carbonate, which is 8.4 gpg. That is hard on the USGS scale. It comes from 21 samples at 20 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 5.3 and 10.7 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: medium (how it is measured).
What to do next
At 8.4 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 Missoula 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 1.9 to 13.2 gpg
The softest single sample on record in Missoula County was 33.1 mg/L and the hardest 226 mg/L, a 7-fold gap. The top quarter of sites read above 10.7 gpg and the bottom quarter below 5.3 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 8.4 gpg, rivers and lakes 4.5 gpg
21 groundwater samples from 20 wells put the median at 144.5 mg/L. 2,350 surface samples from 163 sites put it at 76.2 mg/L. In Missoula County the wells come out 3.9 gpg harder. Groundwater sits in contact with rock for years and picks up calcium and magnesium as it goes, so wells usually read harder. 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 184 lb of salt a year (5 bags of 40 lb, about $33), 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 $133 a year.
Sizing at 8.4 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 504 | 24,000 | 61 lb |
| 2 | 1,008 | 24,000 | 123 lb |
| 4 | 2,016 | 24,000 | 245 lb |
| 6 | 3,024 | 24,000 | 368 lb |
Missoula County against the rest of Montana
Among the 56 Montana counties with data, Missoula County is number 46 of 56 counting from the hardest. Across the whole country it is harder than 44% of counties.
Softest in Montana: Lincoln County at 3.4 gpg. Hardest: Rosebud County at 138.9 gpg. Closest to Missoula County: Hill County (8.7), Jefferson County (8.1), Deer Lodge County (8.9).