How hard is the water in Ontonagon County, MI?
4.2 grains per gallon
Optional: a softener helps, but plenty of homes skip it.
The median hardness measured in Ontonagon County, MI is 72 mg/L as calcium carbonate, which is 4.2 gpg. That is moderately hard on the USGS scale. It comes from 200 samples at 10 sites between 1990 and 2024, drawn from every sampling site in the county, wells and surface water together.
How much it varies here
Half the sites came in between 3.4 and 5.6 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 4.2 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 Ontonagon 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 2.6 to 8.2 gpg
The softest single sample on record in Ontonagon County was 45 mg/L and the hardest 140 mg/L, a 3-fold gap. The top quarter of sites read above 5.6 gpg and the bottom quarter below 3.4 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 91 lb of salt a year (3 bags of 40 lb, about $16), 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 $116 a year.
Sizing at 4.2 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 252 | 24,000 | 31 lb |
| 2 | 504 | 24,000 | 61 lb |
| 4 | 1,008 | 24,000 | 123 lb |
| 6 | 1,512 | 24,000 | 184 lb |
Ontonagon County against the rest of Michigan
Among the 82 Michigan counties with data, Ontonagon County is number 72 of 82 counting from the hardest. Across the whole country it is harder than 27% of counties.
Softest in Michigan: Luce County at 1.9 gpg. Hardest: Wayne County at 47.4 gpg. Closest to Ontonagon County: Marquette County (4.2), Schoolcraft County (4.4), Otsego County (4.7).