Hardest Water in Illinois
31 cities ranked by water hardness. Yorkville tops the list at 380 PPM.
Illinois's water hardness varies significantly by city and water source. The state average across our database is 253 PPM, which is very hard. Most Illinois households will benefit from a water softener. 100% of cities we track in Illinois have hardness above 120 PPM.
Yorkville has the hardest water at 380 PPM (22.2 GPG). At this level, expect visible scale on faucets, reduced water heater efficiency, and higher soap usage. A salt-based water softener typically pays for itself within 12-18 months in energy and consumable savings.
| # | City | PPM | GPG | Level | Softener? |
|---|---|---|---|---|---|
| 1 | Yorkville | 380 | 22.2 | Extremely Hard | Yes |
| 2 | Washington | 380 | 22.2 | Extremely Hard | Yes |
| 3 | Bolingbrook | 350 | 20.5 | Extremely Hard | Yes |
| 4 | Plainfield | 350 | 20.5 | Extremely Hard | Yes |
| 5 | DeKalb South | 340 | 19.9 | Extremely Hard | Yes |
| 6 | Orland Park | 320 | 18.7 | Extremely Hard | Yes |
| 7 | Wheaton | 310 | 18.1 | Extremely Hard | Yes |
| 8 | Libertyville | 310 | 18.1 | Extremely Hard | Yes |
| 9 | Naperville South | 310 | 18.1 | Extremely Hard | Yes |
| 10 | Palatine | 300 | 17.5 | Extremely Hard | Yes |
| 11 | Arlington Heights | 290 | 17 | Extremely Hard | Yes |
| 12 | Bloomington | 289 | 16.9 | Extremely Hard | Yes |
| 13 | Champaign | 285 | 16.7 | Extremely Hard | Yes |
| 14 | Normal | 285 | 16.7 | Extremely Hard | Yes |
| 15 | Urbana | 280 | 16.4 | Extremely Hard | Yes |
| 16 | Joliet | 279 | 16.3 | Extremely Hard | Yes |
| 17 | DeKalb | 270 | 15.8 | Extremely Hard | Yes |
| 18 | Peoria | 231 | 13.5 | Very Hard | Yes |
| 19 | Springfield | 227 | 13.3 | Very Hard | Yes |
| 20 | Belleville | 225 | 13.2 | Very Hard | Yes |
| 21 | Naperville | 220 | 12.9 | Very Hard | Yes |
| 22 | Elgin | 191 | 11.2 | Very Hard | Yes |
| 23 | Decatur | 191 | 11.2 | Very Hard | Yes |
| 24 | Rockford | 185 | 10.8 | Very Hard | Yes |
| 25 | Schaumburg | 175 | 10.2 | Hard | Recommended |
| 26 | Waukegan | 165 | 9.6 | Hard | Recommended |
| 27 | Cicero | 150 | 8.8 | Hard | Recommended |
| 28 | Oak Park | 145 | 8.5 | Hard | Recommended |
| 29 | Chicago | 140 | 8.2 | Hard | Recommended |
| 30 | Evanston | 140 | 8.2 | Hard | Recommended |
| 31 | Oak Park South | 140 | 8.2 | Hard | Recommended |
Frequently Asked Questions
What is the average water hardness in Illinois?
Across 31 cities in our database, the average water hardness in Illinois is 253 PPM (14.8 GPG). This ranges from 140 PPM in Oak Park South to 380 PPM in Yorkville.
Do I need a water softener in Illinois?
It depends on your city. 100% of Illinois cities in our database (31 of 31) have hardness above 120 PPM where a softener provides measurable benefit. Check your specific city above.
Which Illinois city has the softest water?
Oak Park South has the softest water in Illinois at 140 PPM (8.2 GPG). No water softener is needed at this level.
What causes hard water in Illinois?
Hard water in Illinois is caused by dissolved calcium and magnesium from the local geology. Limestone and dolomite bedrock are the primary sources, dissolving minerals into groundwater and surface water as it flows through the rock.