How hard is the water in Clark County, MO?
12.1 grains per gallon
A softener will pay its way here.
The median hardness measured in Clark County, MO is 207 mg/L as calcium carbonate, which is 12.1 gpg. That is very hard on the USGS scale. It comes from 83 samples at 7 sites between 1990 and 2023, drawn from every sampling site in the county, wells and surface water together.
How much it varies here
Half the sites came in between 11.1 and 13.2 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 12.1 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 7.4 to 15.2 gpg
The softest single sample on record in Clark County was 127 mg/L and the hardest 261 mg/L, a 2-fold gap. The top quarter of sites read above 13.2 gpg and the bottom quarter below 11.1 gpg.
Wells 12.9 gpg, rivers and lakes 12 gpg
1 groundwater samples from 1 wells put the median at 221 mg/L. 82 surface samples from 6 sites put it at 206 mg/L. In Clark County the wells come out 0.9 gpg harder. Groundwater sits in contact with rock for years and picks up calcium and magnesium as it goes, so wells usually read harder. The two sources are close, so the county figure should hold whichever one your tap is on.
What a softener would cost to run
For a household of 3, a 24,000-grain unit covers a week between regenerations. Expect about 263 lb of salt a year (7 bags of 40 lb, about $47), 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 $147 a year.
Sizing at 12.1 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 726 | 24,000 | 88 lb |
| 2 | 1,452 | 24,000 | 177 lb |
| 4 | 2,904 | 24,000 | 353 lb |
| 6 | 4,356 | 32,000 | 530 lb |
Clark County against the rest of Missouri
Among the 110 Missouri counties with data, Clark County is number 50 of 110 counting from the hardest. Across the whole country it is harder than 59% of counties.
Softest in Missouri: Livingston County at 4.1 gpg. Hardest: Reynolds County at 96.7 gpg. Closest to Clark County: Ozark County (12), Jasper County (12.1), St. Louis city (12.1).