How hard is the water in Corson County, SD?

1.2 grains per gallon

You do not need a softener here.

The median hardness measured in Corson County, SD is 21 mg/L as calcium carbonate, which is 1.2 gpg. That is soft on the USGS scale. It comes from 13 samples at 11 sites between 1990 and 2018, 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 0.9 and 1.8 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: medium (how it is measured).

What to do next

You can skip the softener. At 1.2 gpg the most a softener would fix is the odd water spot. If a salesperson in Corson County says otherwise, ask to see their reading in grains per gallon and compare it with this one.

More on when a softener is not worth it.

From 0.5 to 11.9 gpg

The softest single sample on record in Corson County was 8.5 mg/L and the hardest 204 mg/L, a 24-fold gap. The top quarter of sites read above 1.8 gpg and the bottom quarter below 0.9 gpg. So even in a soft county, a handful of wells here produce water hard enough to scale a heater.

Wells 1.2 gpg, rivers and lakes 10.5 gpg

13 groundwater samples from 11 wells put the median at 21.2 mg/L. 164 surface samples from 5 sites put it at 180 mg/L. In Corson County the rivers and lakes come out 9.3 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.

Corson County against the rest of South Dakota

Among the 55 South Dakota counties with data, Corson County is number 53 of 55 counting from the hardest. Across the whole country it is harder than 9% of counties.

Softest in South Dakota: Dewey County at 0.5 gpg. Hardest: Hanson County at 84.7 gpg. Closest to Corson County: Dewey County (0.5), Ziebach County (0.5), Jackson County (2.7).