How hard is the water in Gregory County, SD?

11.1 grains per gallon

A softener will pay its way here.

The median hardness measured in Gregory County, SD is 190 mg/L as calcium carbonate, which is 11.1 gpg. That is very hard on the USGS scale. It comes from 21 samples at 5 sites between 2003 and 2014, drawn from every sampling site in the county, wells and surface water together.

How much it varies here

Half the sites came in between 10.5 and 12 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

At 11.1 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 5.7 to 24.1 gpg

The softest single sample on record in Gregory County was 97 mg/L and the hardest 413 mg/L, a 4-fold gap. The top quarter of sites read above 12 gpg and the bottom quarter below 10.5 gpg.

What a softener would cost to run

For a household of 3, a 24,000-grain unit covers a week between regenerations. Expect about 242 lb of salt a year (7 bags of 40 lb, about $44), 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 $144 a year.

Sizing at 11.1 gpg

Gregory County against the rest of South Dakota

Among the 55 South Dakota counties with data, Gregory County is number 45 of 55 counting from the hardest. Across the whole country it is harder than 55% of counties.

Softest in South Dakota: Dewey County at 0.5 gpg. Hardest: Hanson County at 84.7 gpg. Closest to Gregory County: Brule County (10.8), Beadle County (10.5), Tripp County (9.9).