How hard is the water in Hennepin County, MN?
23.6 grains per gallon
A softener will pay its way here.
The median hardness measured in Hennepin County, MN is 404 mg/L as calcium carbonate, which is 23.6 gpg. That is very hard on the USGS scale. It comes from 193 samples at 90 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 19.7 and 27.2 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 23.6 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 5.6 to 49.1 gpg
The softest single sample on record in Hennepin County was 95.8 mg/L and the hardest 840 mg/L, a 9-fold gap. The top quarter of sites read above 27.2 gpg and the bottom quarter below 19.7 gpg.
Wells 23.6 gpg, rivers and lakes 10.8 gpg
193 groundwater samples from 90 wells put the median at 404.3 mg/L. 1,675 surface samples from 75 sites put it at 185.5 mg/L. In Hennepin County the wells come out 12.8 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 516 lb of salt a year (13 bags of 40 lb, about $93), 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 $193 a year.
Sizing at 23.6 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,416 | 24,000 | 172 lb |
| 2 | 2,832 | 24,000 | 345 lb |
| 4 | 5,664 | 40,000 | 689 lb |
| 6 | 8,496 | 64,000 | 1,034 lb |
Hennepin County against the rest of Minnesota
Among the 87 Minnesota counties with data, Hennepin County is number 14 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 Hennepin County: Grant County (23.4), Cottonwood County (23.2), St. Louis County (23.2).