How hard is the water in Teton County, MT?
21.7 grains per gallon
A softener will pay its way here.
The median hardness measured in Teton County, MT is 371 mg/L as calcium carbonate, which is 21.7 gpg. That is very hard on the USGS scale. It comes from 65 samples at 36 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 15.6 and 75.3 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: high (how it is measured).
What to do next
At 21.7 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 1.7 to 280.4 gpg
The softest single sample on record in Teton County was 28.6 mg/L and the hardest 4,800 mg/L, a 168-fold gap. The top quarter of sites read above 75.3 gpg and the bottom quarter below 15.6 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 21.7 gpg, rivers and lakes 22.1 gpg
65 groundwater samples from 36 wells put the median at 370.8 mg/L. 210 surface samples from 59 sites put it at 378 mg/L. In Teton County the rivers and lakes come out 0.4 gpg harder. Here the surface water reads harder than the wells, which often points to streams fed by limestone springs or irrigation return flow. 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 32,000-grain unit covers a week between regenerations. Expect about 473 lb of salt a year (12 bags of 40 lb, about $85), 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 $185 a year.
Sizing at 21.7 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,302 | 24,000 | 158 lb |
| 2 | 2,604 | 24,000 | 317 lb |
| 4 | 5,208 | 40,000 | 634 lb |
| 6 | 7,812 | 64,000 | 950 lb |
Teton County against the rest of Montana
Among the 56 Montana counties with data, Teton County is number 22 of 56 counting from the hardest. Across the whole country it is harder than 88% of counties.
Softest in Montana: Lincoln County at 3.4 gpg. Hardest: Rosebud County at 138.9 gpg. Closest to Teton County: Judith Basin County (21.5), McCone County (23.1), Carter County (24).