How hard is the water in Sweet Grass County, MT?
5 grains per gallon
Optional: a softener helps, but plenty of homes skip it.
The median hardness measured in Sweet Grass County, MT is 86 mg/L as calcium carbonate, which is 5 gpg. That is moderately hard on the USGS scale. It comes from 85 samples at 40 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 2.5 and 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: high (how it is measured).
What to do next
At 5 gpg this is your call. Look for white film on glasses and crust on the shower head: if you see little of either, you can live without one. If you do want one, a 24,000-grain unit is enough, so ask for that size rather than a bigger one. Because Sweet Grass County straddles a decision line, check your own tap with a $10 test strip before you spend anything.
More on when a softener is not worth it.
From 0.9 to 12.2 gpg
The softest single sample on record in Sweet Grass County was 15.2 mg/L and the hardest 208 mg/L, a 14-fold gap. The top quarter of sites read above 7 gpg and the bottom quarter below 2.5 gpg.
What a softener would cost to run
For a household of 3, a 24,000-grain unit covers a week between regenerations. Expect about 110 lb of salt a year (3 bags of 40 lb, about $20), 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 $120 a year.
Sizing at 5 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 300 | 24,000 | 37 lb |
| 2 | 600 | 24,000 | 73 lb |
| 4 | 1,200 | 24,000 | 146 lb |
| 6 | 1,800 | 24,000 | 219 lb |
Sweet Grass County against the rest of Montana
Among the 56 Montana counties with data, Sweet Grass County is number 52 of 56 counting from the hardest. Across the whole country it is harder than 31% of counties.
Softest in Montana: Lincoln County at 3.4 gpg. Hardest: Rosebud County at 138.9 gpg. Closest to Sweet Grass County: Park County (5.1), Ravalli County (4.6), Mineral County (4.5).