How hard is the water in Arlington Heights, IL?

Tap water hardness
115mg/L
6.7gpg
Moderately hard

Reported by Arlington Heights · April 2025

IL typical
139 mg/L
EPA health violations since 2016
0
Softener for 3 people
24k grain
Data
Utility report

Arlington Heights water measures 115 mg/L (6.7 gpg) of hardness, moderately hard by USGS standards. The number comes from Arlington Heights, dated April 2025.

Arlington Heights on the hardness scale, with nearby cities
060120180240300360+IL typical 139Mount Prospect: 112 mg/LMount Prospect 112Des Plaines: 126 mg/LDes Plaines 126Schaumburg: 130 mg/LSchaumburg 130Northbrook: 131 mg/LNorthbrook 131Wheeling: 132 mg/LWheeling 132Elk Grove Village: 141 mg/LElk Grove Village 141Buffalo Grove: 154 mg/LBuffalo Grove 154Rolling Meadows: 229 mg/LRolling Meadows 229Palatine: 350 mg/LPalatine 350Lincolnshire: 380 mg/LLincolnshire 380Arlington Heights 115mg/L as calcium carbonate060120180240300360+IL 139Mount Prospect: 112 mg/LMount Pros. 112Des Plaines: 126 mg/LDes Plaines 126Wheeling: 132 mg/LWheeling 132Buffalo Grove: 154 mg/LBuffalo Gr. 154Rolling Meadows: 229 mg/LRolling Me. 229Palatine: 350 mg/LPalatine 350115 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

At 115 mg/L, Arlington Heights is 24 mg/L below the typical Illinois figure of 139. Of the 10 nearest cities we track, 1 has softer water and 9 have harder. The range nearby runs from 112 mg/L in Mount Prospect to 380 in Lincolnshire.

What 115 mg/L means at home

You may see faint white spots on glasses and shower doors after the water dries.

Scale builds up slowly. A kettle or coffee maker needs descaling now and then, maybe every few months.

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

Optional. Plenty of households at this level live with it and descale the kettle now and then.

Water softener

Worth a look if spots on glass bother you, or if your tankless water heater manual asks for softer water.

Carbon filter

Improves taste and removes chlorine. It leaves calcium and magnesium in place.

Softener size for Arlington Heights

3 people × 75 gallons a day × 6.7 gpg = 1,514 grains a day. A 24,000-grain unit regenerates about every 15 days.

Size it for your household

EPA record for Arlington Heights's water system

Arlington Heights · PWSID IL0314030

No health-based violations since 2016

Serves about 73,320 people from surface water.

Health-based
0
Monitoring or reporting
25
Open now
3

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 Arlington Heights water hard?

Somewhat. It measures about 115 mg/L (6.7 grains per gallon), which the USGS classes as moderately hard.

What is the water hardness in Arlington Heights in grains per gallon?

About 6.7 gpg. One grain per gallon equals 17.1 mg/L, so 115 mg/L divided by 17.1 gives 6.7.

What size water softener do I need in Arlington Heights?

For 3 people using 75 gallons each per day, 6.7 gpg works out to about 1,514 grains a day. A 24,000-grain softener covers that with a regeneration about every 15 days.

Has the Arlington Heights water system had EPA violations?

EPA records show no health-based violations for Arlington Heights since 2016. There were also 25 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, April 22, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.