Hard water in Manhattan, IL

Tap water hardness
372mg/L
21.8gpg
Very hard

Reported by Aqua Illinois-Willowbrook · August 2023

IL typical
139 mg/L
EPA health violations since 2016
0
Softener for 3 people
48k grain
Data
Utility report

Manhattan water measures 372 mg/L (21.8 gpg) of hardness, very hard by USGS standards. The number comes from Aqua Illinois-Willowbrook, dated August 2023.

Manhattan on the hardness scale, with nearby cities
060120180240300360+IL typical 139Mokena: 91 mg/LMokena 91New Lenox: 137 mg/LNew Lenox 137Richton Park: 206 mg/LRichton Park 206Joliet: 244 mg/LJoliet 244Frankfort: 287 mg/LFrankfort 287Homer Glen: 287 mg/LHomer Glen 287Tinley Park: 300 mg/LTinley Park 300Monee: 558 mg/LMonee 558Lockport: 458 mg/LLockport 458Crest Hill: 465 mg/LCrest Hill 465Manhattan 372off the scalemg/L as calcium carbonate060120180240300360+IL 139Mokena: 91 mg/LMokena 91New Lenox: 137 mg/LNew Lenox 137Joliet: 244 mg/LJoliet 244Frankfort: 287 mg/LFrankfort 287Monee: 558 mg/LMonee 558Lockport: 458 mg/LLockport 458372 mg/Loff the scalemg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

At 372 mg/L, Manhattan is 233 mg/L above the typical Illinois figure of 139. Of the 10 nearest cities we track, 7 have softer water and 3 have harder. The range nearby runs from 91 mg/L in Mokena to 558 in Monee.

What 372 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 372 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.

Softener size for Manhattan

3 people × 75 gallons a day × 21.8 gpg = 4,894 grains a day. A 48,000-grain unit regenerates about every 9 days.

Size it for your household

EPA record for Manhattan's water system

Aqua Illinois-Willowbrook · PWSID IL1977870

No health-based violations since 2016

Serves about 5,100 people from groundwater.

Health-based
0
Monitoring or reporting
4
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 Manhattan water hard?

Yes. It measures about 372 mg/L (21.8 grains per gallon), which the USGS classes as very hard.

What is the water hardness in Manhattan in grains per gallon?

About 21.8 gpg. One grain per gallon equals 17.1 mg/L, so 372 mg/L divided by 17.1 gives 21.8.

What size water softener do I need in Manhattan?

For 3 people using 75 gallons each per day, 21.8 gpg works out to about 4,894 grains a day. A 48,000-grain softener covers that with a regeneration about every 9 days.

Has the Manhattan water system had EPA violations?

EPA records show no health-based violations for Aqua Illinois-Willowbrook since 2016. There were also 4 monitoring or reporting violations, which are about late or missing tests and notices.

Nearby cities

All 192 cities in Illinois

Hardness data: TapWaterData US Water Hardness (utility report, August 28, 2023), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.