How Hard Is Rockford's Water? Hardness by Town (Illinois EPA Data)
Updated
Short answer
The table
Figures are the median of total hardness (as calcium carbonate) in Illinois EPA laboratory results for samples taken at each system's wells, listed in the state's Drinking Water Watch database. Where the state reported calcium but not total hardness, we show calcium hardness (calcium times 2.497), which is a floor: magnesium would add to it.
| Water system | Hardness (mg/L) | Grains/gal | Samples | Serves |
|---|---|---|---|---|
| Aqua Illinois, Candlewick division | 460 (very hard) | 26.9 | 3, 2022 to 2026 | Candlewick Lake |
| City of Rockford | 377 (very hard) | 22 | 13, 2022 to 2026 | Rockford |
| City of Belvidere | 371 (very hard) | 21.7 | 5, 2009 to 2015 | Belvidere |
| North Park Public Water District | 362 (very hard) | 21.2 | 3, 2022 to 2026 | Machesney Park, Roscoe |
| Village of Rockton | 324 (very hard) | 18.9 | 3, 2024 to 2026 | Rockton |
| Village of Cherry Valley | 321 (very hard) | 18.8 | 3, 2022 to 2026 | Cherry Valley |
| City of Loves Park | 310 (very hard) | 18.1 | 1, 2018 | Loves Park |
| Village of Pecatonica | 307 (very hard) | 18 | 3, 2019 to 2021 | Pecatonica |
| Village of Capron | 300 (very hard) | 17.5 | 1, 2018 | Capron |
| Village of Winnebago | 269 (very hard) | 15.7 | 3, 2022 to 2026 | Winnebago |
| Poplar Grove South | at least 265 (very hard) | 15.5 | calcium only, 2024 to 2024 | Poplar Grove |
| Poplar Grove West (Countryside) | at least 206 (very hard) | 12 | calcium only, 2023 to 2023 | Poplar Grove |
| Village of Poplar Grove | at least 201 (very hard) | 11.8 | calcium only, 2020 to 2023 | Poplar Grove |
| Village of Durand | at least 165 (hard) | 9.6 | calcium only, 2021 to 2024 | Durand |
| City of Beloit, WI (bought by South Beloit) | 280 to 400 (very hard) | 16 to 23 | 2024 water quality report | South Beloit |
How to read it
The USGS classes water at 0 to 60 mg/L as soft, 61 to 120 as moderately hard, 121 to 180 as hard and more than 180 as very hard (USGS). One grain per gallon is 17.1 mg/L. Water softener and dishwasher settings use grains.
These are source-water samples from wells, so treat them as your town's typical water, not your tap on a given day. The Rockford Water Division's own figure is 9 to 21 grains per gallon from its 39 wells (City of Rockford), and the City of Beloit reports 280 to 400 mg/L (16 to 23 grains) for the water South Beloit buys (City of Beloit).
Private wells
Rural homes on their own wells are not in this data. In Winnebago County, the Health Department routes private well testing through the City of Rockford Environmental Laboratory (Winnebago County Health Department). In Boone County the standard test covers bacteria and nitrates, with other tests a la carte (Boone County Health Department).
Why it matters for appliances
See what hard water does to appliances. Every town page in the service area shows its own system's number.
Quick answers
Is Rockford's water hard?
Very hard. Illinois EPA lab samples of Rockford's wells had a median of 377 mg/L of total hardness, and the city gives 9 to 21 grains per gallon.
What is the softest water in the area?
Of the systems with state hardness data, the Village of Winnebago's was the lowest, and it is still very hard by the USGS scale.
How do I convert mg/L to grains per gallon?
Divide by 17.1. For example, 342 mg/L is 20 grains per gallon.
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