How hard is the water in Oglala Lakota County, SD?
8.2 grains per gallon
A softener is worth it here.
The median hardness measured in Oglala Lakota County, SD is 141 mg/L as calcium carbonate, which is 8.2 gpg. That is hard on the USGS scale. It comes from 77 samples at 50 sites between 1990 and 2010, 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 6.3 and 10.3 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 8.2 gpg a softener is worth getting, mainly to protect the water heater and cut soap use. Get at least two quotes, ask each installer what grain capacity they are fitting, and check it against the sizing table below. Because Oglala Lakota 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 1.0 to 58.4 gpg
The softest single sample on record in Oglala Lakota County was 17.8 mg/L and the hardest 1,000 mg/L, a 56-fold gap. The top quarter of sites read above 10.3 gpg and the bottom quarter below 6.3 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 8.2 gpg, rivers and lakes 17 gpg
77 groundwater samples from 50 wells put the median at 140.5 mg/L. 36 surface samples from 5 sites put it at 291 mg/L. In Oglala Lakota County the rivers and lakes come out 8.8 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 179 lb of salt a year (5 bags of 40 lb, about $32), 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 $132 a year.
Sizing at 8.2 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 492 | 24,000 | 60 lb |
| 2 | 984 | 24,000 | 120 lb |
| 4 | 1,968 | 24,000 | 239 lb |
| 6 | 2,952 | 24,000 | 359 lb |
Oglala Lakota County against the rest of South Dakota
Among the 55 South Dakota counties with data, Oglala Lakota County is number 50 of 55 counting from the hardest. Across the whole country it is harder than 44% of counties.
Softest in South Dakota: Dewey County at 0.5 gpg. Hardest: Hanson County at 84.7 gpg. Closest to Oglala Lakota County: Todd County (8.3), Tripp County (9.9), Beadle County (10.5).