How hard is the water in Knox County, IL?
19.1 grains per gallon
A softener will pay its way here.
The median hardness measured in Knox County, IL is 326 mg/L as calcium carbonate, which is 19.1 gpg. That is very hard on the USGS scale. It comes from 120 samples at 18 sites between 1990 and 2002, drawn from every sampling site in the county, wells and surface water together.
How much it varies here
Half the sites came in between 16.4 and 20.7 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 19.1 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 12.2 to 32.2 gpg
The softest single sample on record in Knox County was 209 mg/L and the hardest 551 mg/L, a 3-fold gap. The top quarter of sites read above 20.7 gpg and the bottom quarter below 16.4 gpg.
Wells 16.4 gpg, rivers and lakes 19.3 gpg
1 groundwater samples from 1 wells put the median at 280 mg/L. 118 surface samples from 16 sites put it at 329.8 mg/L. In Knox County the rivers and lakes come out 2.9 gpg harder. Here the surface water reads harder than the wells, which often points to streams fed by limestone springs or irrigation return flow. 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 32,000-grain unit covers a week between regenerations. Expect about 416 lb of salt a year (11 bags of 40 lb, about $75), 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 $175 a year.
Sizing at 19.1 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,146 | 24,000 | 139 lb |
| 2 | 2,292 | 24,000 | 279 lb |
| 4 | 4,584 | 40,000 | 558 lb |
| 6 | 6,876 | 64,000 | 837 lb |
Knox County against the rest of Illinois
Among the 102 Illinois counties with data, Knox County is number 39 of 102 counting from the hardest. Across the whole country it is harder than 82% of counties.
Softest in Illinois: Pope County at 4.3 gpg. Hardest: Cook County at 34.8 gpg. Closest to Knox County: Calhoun County (19.3), Vermilion County (18.7), Winnebago County (18.7).