How hard is the water in Rock Island County, IL?
17.3 grains per gallon
A softener will pay its way here.
The median hardness measured in Rock Island County, IL is 296 mg/L as calcium carbonate, which is 17.3 gpg. That is very hard on the USGS scale. It comes from 14 samples at 5 sites between 1990 and 2017, 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 16.4 and 19.9 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: medium (how it is measured).
What to do next
At 17.3 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 12.9 to 22.0 gpg
The softest single sample on record in Rock Island County was 220 mg/L and the hardest 377 mg/L, a 2-fold gap. The top quarter of sites read above 19.9 gpg and the bottom quarter below 16.4 gpg.
Wells 17.3 gpg, rivers and lakes 18.8 gpg
14 groundwater samples from 5 wells put the median at 296 mg/L. 101 surface samples from 3 sites put it at 322 mg/L. In Rock Island County the rivers and lakes come out 1.5 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 24,000-grain unit covers a week between regenerations. Expect about 378 lb of salt a year (10 bags of 40 lb, about $68), 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 $168 a year.
Sizing at 17.3 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,038 | 24,000 | 126 lb |
| 2 | 2,076 | 24,000 | 253 lb |
| 4 | 4,152 | 32,000 | 505 lb |
| 6 | 6,228 | 48,000 | 758 lb |
Rock Island County against the rest of Illinois
Among the 102 Illinois counties with data, Rock Island County is number 51 of 102 counting from the hardest. Across the whole country it is harder than 77% of counties.
Softest in Illinois: Pope County at 4.3 gpg. Hardest: Cook County at 34.8 gpg. Closest to Rock Island County: Mercer County (17.3), Cumberland County (17.2), Mason County (17.5).