How hard is the water in Mercer County, ND?
13.9 grains per gallon
A softener will pay its way here.
The median hardness measured in Mercer County, ND is 238 mg/L as calcium carbonate, which is 13.9 gpg. That is very hard on the USGS scale. It comes from 871 samples at 30 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 11.6 and 20.5 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 13.9 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 0.0 to 44.9 gpg
The softest single sample on record in Mercer County was 0.3 mg/L and the hardest 769 mg/L, a 2,563-fold gap. The top quarter of sites read above 20.5 gpg and the bottom quarter below 11.6 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 10.8 gpg, rivers and lakes 13.9 gpg
4 groundwater samples from 2 wells put the median at 184.5 mg/L. 867 surface samples from 28 sites put it at 237.5 mg/L. In Mercer County the rivers and lakes come out 3.1 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 303 lb of salt a year (8 bags of 40 lb, about $55), 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 $155 a year.
Sizing at 13.9 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 834 | 24,000 | 101 lb |
| 2 | 1,668 | 24,000 | 203 lb |
| 4 | 3,336 | 24,000 | 406 lb |
| 6 | 5,004 | 40,000 | 609 lb |
Mercer County against the rest of North Dakota
Among the 53 North Dakota counties with data, Mercer County is number 43 of 53 counting from the hardest. Across the whole country it is harder than 66% of counties.
Softest in North Dakota: Hettinger County at 1.1 gpg. Hardest: Walsh County at 54 gpg. Closest to Mercer County: Griggs County (14.3), Burke County (13.3), Benson County (14.9).