How hard is the water in Madison County, IL?
28.7 grains per gallon
A softener will pay its way here.
The median hardness measured in Madison County, IL is 492 mg/L as calcium carbonate, which is 28.7 gpg. That is very hard on the USGS scale. It comes from 43 samples at 16 sites between 1990 and 2023, drawn from groundwater wells, which is what most taps and private wells in the county draw on.
How much it varies here
Half the sites came in between 22.9 and 34.2 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 28.7 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 16.4 to 229.0 gpg
The softest single sample on record in Madison County was 280 mg/L and the hardest 3,920 mg/L, a 14-fold gap. The top quarter of sites read above 34.2 gpg and the bottom quarter below 22.9 gpg.
Wells 28.7 gpg, rivers and lakes 16.8 gpg
43 groundwater samples from 16 wells put the median at 492 mg/L. 493 surface samples from 35 sites put it at 287.5 mg/L. In Madison County the wells come out 11.9 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 40,000-grain unit covers a week between regenerations. Expect about 628 lb of salt a year (16 bags of 40 lb, about $113), 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 $213 a year.
Sizing at 28.7 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,722 | 24,000 | 210 lb |
| 2 | 3,444 | 32,000 | 419 lb |
| 4 | 6,888 | 64,000 | 838 lb |
| 6 | 10,332 | 80,000 | 1,257 lb |
Madison County against the rest of Illinois
Among the 102 Illinois counties with data, Madison County is number 3 of 102 counting from the hardest. Across the whole country it is harder than 94% of counties.
Softest in Illinois: Pope County at 4.3 gpg. Hardest: Cook County at 34.8 gpg. Closest to Madison County: Perry County (30.8), Kane County (25.7), Lee County (25.4).