How hard is the water in DeKalb County, IL?
19.7 grains per gallon
A softener will pay its way here.
The median hardness measured in DeKalb County, IL is 337 mg/L as calcium carbonate, which is 19.7 gpg. That is very hard on the USGS scale. It comes from 105 samples at 11 sites between 1990 and 2017, drawn from every sampling site in the county, wells and surface water together.
How much it varies here
Half the sites came in between 17.4 and 20.9 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 19.7 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 13.4 to 24.5 gpg
The softest single sample on record in DeKalb County was 230 mg/L and the hardest 420 mg/L, a 2-fold gap. The top quarter of sites read above 20.9 gpg and the bottom quarter below 17.4 gpg.
Wells 14 gpg, rivers and lakes 20.2 gpg
10 groundwater samples from 3 wells put the median at 240 mg/L. 95 surface samples from 8 sites put it at 345.5 mg/L. In DeKalb County the rivers and lakes come out 6.2 gpg harder. Here the surface water reads harder than the wells, which often points to streams fed by limestone springs or irrigation return flow. A utility here that draws from the aquifer can deliver noticeably different water from a private well next door.
What a softener would cost to run
For a household of 3, a 32,000-grain unit covers a week between regenerations. Expect about 430 lb of salt a year (11 bags of 40 lb, about $77), 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 $177 a year.
Sizing at 19.7 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,182 | 24,000 | 144 lb |
| 2 | 2,364 | 24,000 | 288 lb |
| 4 | 4,728 | 40,000 | 575 lb |
| 6 | 7,092 | 64,000 | 863 lb |
DeKalb County against the rest of Illinois
Among the 102 Illinois counties with data, DeKalb County is number 35 of 102 counting from the hardest. Across the whole country it is harder than 83% of counties.
Softest in Illinois: Pope County at 4.3 gpg. Hardest: Cook County at 34.8 gpg. Closest to DeKalb County: Ford County (19.7), Menard County (19.6), Peoria County (19.8).