How hard is the water in Fergus County, MT?
28.9 grains per gallon
A softener will pay its way here.
The median hardness measured in Fergus County, MT is 495 mg/L as calcium carbonate, which is 28.9 gpg. That is very hard on the USGS scale. It comes from 238 samples at 105 sites between 1990 and 2026, drawn from every sampling site in the county, wells and surface water together.
How much it varies here
Half the sites came in between 18 and 68.3 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 28.9 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 1.3 to 286.2 gpg
The softest single sample on record in Fergus County was 22.1 mg/L and the hardest 4,900 mg/L, a 222-fold gap. The top quarter of sites read above 68.3 gpg and the bottom quarter below 18 gpg. So even here some sites draw water soft enough to need nothing at all.
What a softener would cost to run
For a household of 3, a 40,000-grain unit covers a week between regenerations. Expect about 631 lb of salt a year (16 bags of 40 lb, about $114), 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 $214 a year.
Sizing at 28.9 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,734 | 24,000 | 211 lb |
| 2 | 3,468 | 32,000 | 422 lb |
| 4 | 6,936 | 64,000 | 844 lb |
| 6 | 10,404 | 80,000 | 1,266 lb |
Fergus County against the rest of Montana
Among the 56 Montana counties with data, Fergus County is number 15 of 56 counting from the hardest. Across the whole country it is harder than 94% of counties.
Softest in Montana: Lincoln County at 3.4 gpg. Hardest: Rosebud County at 138.9 gpg. Closest to Fergus County: Richland County (29.1), Yellowstone County (27.7), Dawson County (30.2).