How hard is the water in St. Clair County, IL?
24 grains per gallon
A softener will pay its way here.
The median hardness measured in St. Clair County, IL is 411 mg/L as calcium carbonate, which is 24 gpg. That is very hard on the USGS scale. It comes from 21 samples at 6 sites between 1990 and 2015, 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 20.7 and 27 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 24 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 18.6 to 58.3 gpg
The softest single sample on record in St. Clair County was 319 mg/L and the hardest 998 mg/L, a 3-fold gap. The top quarter of sites read above 27 gpg and the bottom quarter below 20.7 gpg.
Wells 24 gpg, rivers and lakes 16.4 gpg
21 groundwater samples from 6 wells put the median at 411.3 mg/L. 279 surface samples from 16 sites put it at 281.5 mg/L. In St. Clair County the wells come out 7.6 gpg harder. Groundwater sits in contact with rock for years and picks up calcium and magnesium as it goes, so wells usually read harder. 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 32,000-grain unit covers a week between regenerations. Expect about 525 lb of salt a year (14 bags of 40 lb, about $94), 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 $194 a year.
Sizing at 24 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,440 | 24,000 | 175 lb |
| 2 | 2,880 | 24,000 | 350 lb |
| 4 | 5,760 | 48,000 | 701 lb |
| 6 | 8,640 | 64,000 | 1,051 lb |
St. Clair County against the rest of Illinois
Among the 102 Illinois counties with data, St. Clair County is number 6 of 102 counting from the hardest. Across the whole country it is harder than 91% of counties.
Softest in Illinois: Pope County at 4.3 gpg. Hardest: Cook County at 34.8 gpg. Closest to St. Clair County: Lake County (23.4), McLean County (23.4), McHenry County (23.2).