Hard water in Chicago, IL
Reported by City of Chicago Department of Water Management · October 2024
- IL typical
- 139 mg/L
- EPA health violations since 2016
- 0
- Softener for 3 people
- 24k grain
- Data
- Utility report
Chicago water measures 139 mg/L (8.1 gpg) of hardness, hard by USGS standards. The number comes from City of Chicago Department of Water Management, dated October 2024.
Chicago sits close to the typical Illinois figure of 139 mg/L. Of the 10 nearest cities we track, 4 have softer water and 6 have harder. The range nearby runs from 104 mg/L in River Grove to 229 in Cicero.
What 139 mg/L means at home
Expect white crust on faucets and showerheads, plus spots on dishes that come out of the dishwasher.
Kettles collect scale quickly. Water heaters build up sediment at the bottom of the tank, which makes them work harder over time.
Soap and detergent need a little more to lather, and soap scum shows up in the tub.
Hardness is not a health problem, and EPA sets no limit for it. It is a matter of scale and soap.
What to do about it
At 139 mg/L most of the trouble is scale, and only a few things deal with it.
Ion-exchange water softener
The standard whole-house fix. It swaps calcium and magnesium for sodium or potassium and needs salt plus a drain. Size it with the calculator below.
Salt-free conditioner
No salt and no drain line. It changes how minerals form scale instead of removing them, so water still tests hard.
Reverse osmosis or carbon filter
Under-sink reverse osmosis removes minerals from drinking water only. Plain carbon filters improve taste but do not soften.
3 people × 75 gallons a day × 8.1 gpg = 1,827 grains a day. A 24,000-grain unit regenerates about every 13 days.
EPA record for Chicago's water system
No health-based violations since 2016
Serves about 2,721,308 people from surface water.
- Health-based
- 0
- Monitoring or reporting
- 45
- Open now
- 0
Health-based means a contaminant above its legal limit or a missed treatment step. Monitoring and reporting violations are late or missing tests and notices. Source: EPA ECHO, 2026Q3 export, violations with periods starting 2016 or later. Full EPA record.
Questions
Is Chicago water hard?
Yes. It measures about 139 mg/L (8.1 grains per gallon), which the USGS classes as hard.
What is the water hardness in Chicago in grains per gallon?
About 8.1 gpg. One grain per gallon equals 17.1 mg/L, so 139 mg/L divided by 17.1 gives 8.1.
What size water softener do I need in Chicago?
For 3 people using 75 gallons each per day, 8.1 gpg works out to about 1,827 grains a day. A 24,000-grain softener covers that with a regeneration about every 13 days.
Has the Chicago water system had EPA violations?
EPA records show no health-based violations for Chicago since 2016. There were also 45 monitoring or reporting violations, which are about late or missing tests and notices.
Nearby cities
- Cicero229 mg/LVery hard
- Berwyn111 mg/LModerately hard
- Oak Park229 mg/LVery hard
- Burbank229 mg/LVery hard
- River Forest135 mg/LHard
- Maywood229 mg/LVery hard
- Elmwood Park229 mg/LVery hard
- Oak Lawn229 mg/LVery hard
- La Grange Park129 mg/LHard
- River Grove104 mg/LModerately hard
Hardness data: TapWaterData US Water Hardness (utility report, October 9, 2024), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.