Hard water in Decatur, IL
County estimate from 411 water samples in Macon 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 Decatur put hardness at about 261 mg/L (15.3 gpg), which would be very hard on the USGS scale. Treat this as a rough guide: it is the median of 411 samples taken across Macon County, mostly wells and streams, not a test of Decatur's treated tap water. One more reason for caution: EPA lists Decatur's water system as using surface water, which is often softer than the wells behind the county figure.
Decatur sits 122 mg/L above the typical Illinois figure of 139. Of the 10 nearest cities we track, 9 have softer water and 1 has harder. The range nearby runs from 84 mg/L in Savoy to 327 in Normal.
What 261 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 261 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 × 15.3 gpg = 3,434 grains a day. A 32,000-grain unit regenerates about every 9 days.
EPA record for Decatur's water system
No health-based violations since 2016
Serves about 76,122 people from surface water.
- Health-based
- 0
- Monitoring or reporting
- 1
- Open now
- 0
EPA lists this system as serving Decatur.
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 Decatur water hard?
Yes. It measures about 261 mg/L (15.3 grains per gallon), which the USGS classes as very hard.
What is the water hardness in Decatur in grains per gallon?
About 15.3 gpg. One grain per gallon equals 17.1 mg/L, so 261 mg/L divided by 17.1 gives 15.3.
What size water softener do I need in Decatur?
For 3 people using 75 gallons each per day, 15.3 gpg works out to about 3,434 grains a day. A 32,000-grain softener covers that with a regeneration about every 9 days.
Has the Decatur water system had EPA violations?
EPA records show no health-based violations for Decatur since 2016. There were also 1 monitoring or reporting violation, which are about late or missing tests and notices.
Nearby cities
- Mount Zion103 mg/LModerately hard
- Taylorville142 mg/LHard
- Lincoln222 mg/LVery hard
- Springfield120 mg/LModerately hard
- Savoy84 mg/LModerately hard
- Champaign85 mg/LModerately hard
- Mattoon108 mg/LModerately hard
- Urbana84 mg/LModerately hard
- Bloomington89 mg/LModerately hard
- Normal327 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.