How hard is the water in St. Louis County, MN?
23.2 grains per gallon
A softener will pay its way here.
The median hardness measured in St. Louis County, MN is 398 mg/L as calcium carbonate, which is 23.2 gpg. That is very hard on the USGS scale. It comes from 63 samples at 10 sites between 1990 and 2025, 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 17.8 and 26.3 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 23.2 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 9.2 to 40.3 gpg
The softest single sample on record in St. Louis County was 158 mg/L and the hardest 690 mg/L, a 4-fold gap. The top quarter of sites read above 26.3 gpg and the bottom quarter below 17.8 gpg.
Wells 23.2 gpg, rivers and lakes 2.9 gpg
63 groundwater samples from 10 wells put the median at 397.5 mg/L. 2,457 surface samples from 313 sites put it at 49 mg/L. In St. Louis County the wells come out 20.3 gpg harder. Groundwater sits in contact with rock for years and picks up calcium and magnesium as it goes, so wells usually read harder. A utility here that draws from the river can deliver noticeably different water from a private well next door.
What a softener would cost to run
For a household of 3, a 32,000-grain unit covers a week between regenerations. Expect about 507 lb of salt a year (13 bags of 40 lb, about $91), 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 $191 a year.
Sizing at 23.2 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,392 | 24,000 | 169 lb |
| 2 | 2,784 | 24,000 | 339 lb |
| 4 | 5,568 | 40,000 | 677 lb |
| 6 | 8,352 | 64,000 | 1,016 lb |
St. Louis County against the rest of Minnesota
Among the 87 Minnesota counties with data, St. Louis County is number 16 of 87 counting from the hardest. Across the whole country it is harder than 90% of counties.
Softest in Minnesota: Lake County at 1.3 gpg. Hardest: Traverse County at 42.6 gpg. Closest to St. Louis County: Cottonwood County (23.2), Grant County (23.4), Hennepin County (23.6).