How hard is the water in Mellette County, SD?
17 grains per gallon
A softener will pay its way here.
The median hardness measured in Mellette County, SD is 292 mg/L as calcium carbonate, which is 17 gpg. That is very hard on the USGS scale. It comes from 60 samples at 60 sites between 1990 and 2014, 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 9.1 and 40.3 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 17 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 Mellette 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 0.7 to 130.3 gpg
The softest single sample on record in Mellette County was 12.8 mg/L and the hardest 2,230 mg/L, a 174-fold gap. The top quarter of sites read above 40.3 gpg and the bottom quarter below 9.1 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 17 gpg, rivers and lakes 7.7 gpg
60 groundwater samples from 60 wells put the median at 291.5 mg/L. 162 surface samples from 4 sites put it at 132.3 mg/L. In Mellette County the wells come out 9.3 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 24,000-grain unit covers a week between regenerations. Expect about 372 lb of salt a year (10 bags of 40 lb, about $67), 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 $167 a year.
Sizing at 17 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,020 | 24,000 | 124 lb |
| 2 | 2,040 | 24,000 | 248 lb |
| 4 | 4,080 | 32,000 | 496 lb |
| 6 | 6,120 | 48,000 | 745 lb |
Mellette County against the rest of South Dakota
Among the 55 South Dakota counties with data, Mellette County is number 36 of 55 counting from the hardest. Across the whole country it is harder than 76% of counties.
Softest in South Dakota: Dewey County at 0.5 gpg. Hardest: Hanson County at 84.7 gpg. Closest to Mellette County: Lawrence County (17.2), Hughes County (16.4), Faulk County (17.8).