Hard water in Collinsville, IL
County estimate from 1,093 water samples in Madison County · July 2026
- IL typical
- 139 mg/L
- EPA health violations since 2016
- 0
- Softener for 3 people
- 32k grain
- Data
- County estimate
Water samples from around Collinsville put hardness at about 276 mg/L (16.1 gpg), which would be very hard on the USGS scale. Treat this as a rough guide: it is the median of 1,093 samples taken across Madison County, mostly wells and streams, not a test of Collinsville's treated tap water.
Collinsville sits 137 mg/L above the typical Illinois figure of 139. None of the 10 nearest cities we track has harder water. The range nearby runs from 87 mg/L in Edwardsville to 276 in Granite City.
What 276 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 276 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 × 16.1 gpg = 3,632 grains a day. A 32,000-grain unit regenerates about every 8 days.
EPA record for Collinsville's water system
No health-based violations since 2016
Serves about 30,616 people from groundwater.
- Health-based
- 0
- Monitoring or reporting
- 0
- Open now
- 0
EPA lists this system as serving Collinsville.
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 Collinsville water hard?
Yes. It measures about 276 mg/L (16.1 grains per gallon), which the USGS classes as very hard.
What is the water hardness in Collinsville in grains per gallon?
About 16.1 gpg. One grain per gallon equals 17.1 mg/L, so 276 mg/L divided by 17.1 gives 16.1.
What size water softener do I need in Collinsville?
For 3 people using 75 gallons each per day, 16.1 gpg works out to about 3,632 grains a day. A 32,000-grain softener covers that with a regeneration about every 8 days.
Has the Collinsville water system had EPA violations?
EPA records show no health-based violations for Collinsville since 2016.
Nearby cities
- Fairview Heights157 mg/LHard
- Granite City276 mg/LVery hard
- East St. Louis157 mg/LHard
- Edwardsville87 mg/LModerately hard
- Swansea157 mg/LHard
- Shiloh157 mg/LHard
- Cahokia Heights157 mg/LHard
- Belleville157 mg/LHard
- Wood River128 mg/LHard
- East Alton190 mg/LVery hard
Hardness data: TapWaterData US Water Hardness (county estimate, July 4, 2026), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.