How hard is the water in Custer County, MT?
16.8 grains per gallon
A softener will pay its way here.
The median hardness measured in Custer County, MT is 288 mg/L as calcium carbonate, which is 16.8 gpg. That is very hard on the USGS scale. It comes from 645 samples at 34 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 10.2 and 26.6 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 16.8 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. Because Custer 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 4.1 to 80.6 gpg
The softest single sample on record in Custer County was 69.6 mg/L and the hardest 1,380 mg/L, a 20-fold gap. The top quarter of sites read above 26.6 gpg and the bottom quarter below 10.2 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 367 lb of salt a year (10 bags of 40 lb, about $66), 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 $166 a year.
Sizing at 16.8 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,008 | 24,000 | 123 lb |
| 2 | 2,016 | 24,000 | 245 lb |
| 4 | 4,032 | 32,000 | 491 lb |
| 6 | 6,048 | 48,000 | 736 lb |
Custer County against the rest of Montana
Among the 56 Montana counties with data, Custer County is number 27 of 56 counting from the hardest. Across the whole country it is harder than 75% of counties.
Softest in Montana: Lincoln County at 3.4 gpg. Hardest: Rosebud County at 138.9 gpg. Closest to Custer County: Blaine County (17), Daniels County (16), Beaverhead County (15.7).