How hard is the water in Petroleum County, MT?
50.9 grains per gallon
A softener will pay its way here.
The median hardness measured in Petroleum County, MT is 871 mg/L as calcium carbonate, which is 50.9 gpg. That is very hard on the USGS scale. It comes from 239 samples at 59 sites between 1990 and 2016, drawn from every sampling site in the county, wells and surface water together.
How much it varies here
Half the sites came in between 26.8 and 94.1 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 50.9 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 2.9 to 291.5 gpg
The softest single sample on record in Petroleum County was 50 mg/L and the hardest 4,990 mg/L, a 100-fold gap. The top quarter of sites read above 94.1 gpg and the bottom quarter below 26.8 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 80,000-grain unit covers a week between regenerations. Expect about 1,111 lb of salt a year (28 bags of 40 lb, about $200), 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 $300 a year.
Sizing at 50.9 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 3,054 | 24,000 | 372 lb |
| 2 | 6,108 | 48,000 | 743 lb |
| 4 | 12,216 | twin tank | 1,486 lb |
| 6 | 18,324 | twin tank | 2,229 lb |
Petroleum County against the rest of Montana
Among the 56 Montana counties with data, Petroleum County is number 6 of 56 counting from the hardest. Across the whole country it is harder than 98% of counties.
Softest in Montana: Lincoln County at 3.4 gpg. Hardest: Rosebud County at 138.9 gpg. Closest to Petroleum County: Roosevelt County (49.5), Cascade County (58.6), Powder River County (60.8).