How hard is the water in Johnson County, MO?

11.7 grains per gallon

A softener will pay its way here.

The median hardness measured in Johnson County, MO is 201 mg/L as calcium carbonate, which is 11.7 gpg. That is very hard on the USGS scale. It comes from 30 samples at 5 sites between 2010 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 11.6 and 12.8 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

At 11.7 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 10.4 to 16.2 gpg

The softest single sample on record in Johnson County was 178 mg/L and the hardest 277 mg/L, a 2-fold gap. The top quarter of sites read above 12.8 gpg and the bottom quarter below 11.6 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 256 lb of salt a year (7 bags of 40 lb, about $46), 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 $146 a year.

Sizing at 11.7 gpg

Johnson County against the rest of Missouri

Among the 110 Missouri counties with data, Johnson County is number 59 of 110 counting from the hardest. Across the whole country it is harder than 57% of counties.

Softest in Missouri: Livingston County at 4.1 gpg. Hardest: Reynolds County at 96.7 gpg. Closest to Johnson County: Dade County (11.7), Lewis County (11.7), Adair County (11.8).