How hard is the water in Douglas County, MO?
11.9 grains per gallon
A softener will pay its way here.
The median hardness measured in Douglas County, MO is 203 mg/L as calcium carbonate, which is 11.9 gpg. That is very hard on the USGS scale. It comes from 183 samples at 23 sites between 1993 and 2026, drawn from every sampling site in the county, wells and surface water together.
How much it varies here
Half the sites came in between 10.9 and 12.6 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 11.9 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 9.3 to 13.8 gpg
The softest single sample on record in Douglas County was 159.5 mg/L and the hardest 237 mg/L, a 1-fold gap. The top quarter of sites read above 12.6 gpg and the bottom quarter below 10.9 gpg.
Wells 13.5 gpg, rivers and lakes 11.9 gpg
1 groundwater samples from 1 wells put the median at 231 mg/L. 182 surface samples from 22 sites put it at 203 mg/L. In Douglas County the wells come out 1.6 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 259 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 11.9 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 714 | 24,000 | 87 lb |
| 2 | 1,428 | 24,000 | 174 lb |
| 4 | 2,856 | 24,000 | 347 lb |
| 6 | 4,284 | 32,000 | 521 lb |
Douglas County against the rest of Missouri
Among the 110 Missouri counties with data, Douglas County is number 55 of 110 counting from the hardest. Across the whole country it is harder than 58% of counties.
Softest in Missouri: Livingston County at 4.1 gpg. Hardest: Reynolds County at 96.7 gpg. Closest to Douglas County: Saline County (11.9), Adair County (11.8), Harrison County (11.8).