How hard is the water in Slope County, ND?
18.5 grains per gallon
A softener will pay its way here.
The median hardness measured in Slope County, ND is 317 mg/L as calcium carbonate, which is 18.5 gpg. That is very hard on the USGS scale. It comes from 174 samples at 7 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 6.5 and 21.6 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: medium (how it is measured).
What to do next
At 18.5 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 Slope 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 1.4 to 40.7 gpg
The softest single sample on record in Slope County was 23.5 mg/L and the hardest 697.5 mg/L, a 30-fold gap. The top quarter of sites read above 21.6 gpg and the bottom quarter below 6.5 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 1.4 gpg, rivers and lakes 19.6 gpg
2 groundwater samples from 2 wells put the median at 23.6 mg/L. 172 surface samples from 5 sites put it at 335.5 mg/L. In Slope County the rivers and lakes come out 18.2 gpg harder. Here the surface water reads harder than the wells, which often points to streams fed by limestone springs or irrigation return flow. A utility here that draws from the aquifer can deliver noticeably different water from a private well next door.
What a softener would cost to run
For a household of 3, a 24,000-grain unit covers a week between regenerations. Expect about 404 lb of salt a year (11 bags of 40 lb, about $73), 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 $173 a year.
Sizing at 18.5 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,110 | 24,000 | 135 lb |
| 2 | 2,220 | 24,000 | 270 lb |
| 4 | 4,440 | 32,000 | 540 lb |
| 6 | 6,660 | 48,000 | 810 lb |
Slope County against the rest of North Dakota
Among the 53 North Dakota counties with data, Slope County is number 31 of 53 counting from the hardest. Across the whole country it is harder than 80% of counties.
Softest in North Dakota: Hettinger County at 1.1 gpg. Hardest: Walsh County at 54 gpg. Closest to Slope County: McIntosh County (18.6), Logan County (18.7), Pembina County (18.2).