How hard is the water in Polk County, MO?
12.2 grains per gallon
A softener will pay its way here.
The median hardness measured in Polk County, MO is 209 mg/L as calcium carbonate, which is 12.2 gpg. That is very hard on the USGS scale. It comes from 179 samples at 22 sites between 1992 and 2025, drawn from every sampling site in the county, wells and surface water together.
How much it varies here
Half the sites came in between 11.9 and 13.4 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: high (how it is measured).
What to do next
At 12.2 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 11.4 to 25.2 gpg
The softest single sample on record in Polk County was 196 mg/L and the hardest 431 mg/L, a 2-fold gap. The top quarter of sites read above 13.4 gpg and the bottom quarter below 11.9 gpg.
Wells 19.3 gpg, rivers and lakes 12.1 gpg
1 groundwater samples from 1 wells put the median at 331 mg/L. 176 surface samples from 20 sites put it at 206.5 mg/L. In Polk County the wells come out 7.2 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 266 lb of salt a year (7 bags of 40 lb, about $48), 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 $148 a year.
Sizing at 12.2 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 732 | 24,000 | 89 lb |
| 2 | 1,464 | 24,000 | 178 lb |
| 4 | 2,928 | 24,000 | 356 lb |
| 6 | 4,392 | 32,000 | 534 lb |
Polk County against the rest of Missouri
Among the 110 Missouri counties with data, Polk County is number 47 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 Polk County: Jasper County (12.1), St. Louis city (12.1), Holt County (12.3).