Hard water in Cary, IL
Reported by Algonquin · September 2025
- IL typical
- 139 mg/L
- EPA health violations since 2016
- 0
- Softener for 3 people
- 48k grain
- Data
- Utility report
The water in Cary carries roughly 378 mg/L of dissolved calcium and magnesium, or 22.1 grains per gallon. That is very hard water. The number comes from Algonquin, dated September 2025.
At 378 mg/L, Cary is 239 mg/L above the typical Illinois figure of 139. Of the 10 nearest cities we track, 6 have softer water and 3 have harder. The range nearby runs from 14 mg/L in West Dundee to 573 in Lake Barrington.
What 378 mg/L means at home
Scale forms fast here. Kettles and coffee makers need regular descaling, and showerheads clog unless you clean them.
Tank water heaters collect mineral sediment that insulates the water from the burner, so flushing the tank matters more than usual.
Dishes and glass shower doors spot easily. Soap scum and a dull film on hair or laundry are common complaints.
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 378 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 × 22.1 gpg = 4,975 grains a day. A 48,000-grain unit regenerates about every 9 days.
EPA record for Cary's water system
No health-based violations since 2016
Serves about 17,826 people from groundwater.
- Health-based
- 0
- Monitoring or reporting
- 2
- Open now
- 1
EPA lists Cary as the system serving Cary. The hardness figure above comes from a different system's report, which TapWaterData uses for Cary.
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 Cary water hard?
Yes. It measures about 378 mg/L (22.1 grains per gallon), which the USGS classes as very hard.
What is the water hardness in Cary in grains per gallon?
About 22.1 gpg. One grain per gallon equals 17.1 mg/L, so 378 mg/L divided by 17.1 gives 22.1.
What size water softener do I need in Cary?
For 3 people using 75 gallons each per day, 22.1 gpg works out to about 4,975 grains a day. A 48,000-grain softener covers that with a regeneration about every 9 days.
Has the Cary water system had EPA violations?
EPA records show no health-based violations for Cary since 2016. There were also 2 monitoring or reporting violations, which are about late or missing tests and notices.
Nearby cities
- Lake in the Hills283 mg/LVery hard
- Lake Barrington573 mg/LVery hard
- Crystal Lake388 mg/LVery hard
- Algonquin378 mg/LVery hard
- Carpentersville67 mg/LModerately hard
- Wauconda146 mg/LHard
- Lake Zurich84 mg/LModerately hard
- West Dundee14 mg/LSoft
- McHenry384 mg/LVery hard
- Lakemoor223 mg/LVery hard
Hardness data: TapWaterData US Water Hardness (utility report, September 2, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.