Northbrook, IL
Above the new 10 ppb level coming in 2027
Latest 90th-percentile lead: 11 ppb (monitoring period 2026-2026). The federal action level is 15 ppb today and drops to 10 ppb in Nov 2027; EPA's health goal is 0. Under the current 15 ppb rule this is not an exceedance, but it is above the 10 ppb action level that takes over in Nov 2027. Test your own tap; filter if your result shows lead.
About Northbrook
Northbrook serves about 34,200 people through 12,554 service connections, which makes it a large system under EPA's size classes. It is owned by a local government (city, town, county or district) and draws surface water, in Cook County, Illinois. EPA system ID: IL0312070; phone on file: 847-664-4139. They can tell you what your service line is made of and whether they pay to replace it.
Every lead result on file
That is up 8 ppb from 3 ppb in the period ending 2025. The highest 90th-percentile result EPA holds for Northbrook is 16 ppb across 8 monitoring periods, 1 of them over the 15 ppb action level.
| Period ending | 90th-percentile lead |
|---|---|
| 2026 | 11 ppb over 10 |
| 2025 | 3 ppb |
| 2025 | 1.3 ppb |
| 2025 | 15 ppb over 10 |
| 2025 | 16 ppb over 15 |
| 2023 | 4.5 ppb |
| 2020 | 4.2 ppb |
| 2017 | 5.73 ppb |
How Northbrook compares
Of the 1,744 Illinois systems with a lead result, the median latest reading is 0 ppb; 22 are over 15 ppb right now and 152 have gone over at some point. Northbrook's 11 ppb sits at the 97th percentile in Illinois and the 98th nationally (higher means more lead).
Nearby utilities
154 other systems share Cook County; 7 of them have a higher latest lead result than Northbrook. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Chicago | 2,721,308 | 6.4 ppb |
| Cicero | 83,000 | 5 ppb |
| Schaumburg | 75,750 | 0.87 ppb |
| Evanston | 74,486 | 6.5 ppb |
| Arlington Heights | 73,320 | 7.6 ppb |
| Palatine | 70,875 | 8.9 ppb |
| Skokie | 66,422 | 9.77 ppb |
| Des Plaines | 60,675 | 5.7 ppb |
| Oak Lawn | 58,362 | 9.3 ppb |
| Orland Park | 58,020 | 0 (not detected) |
Next steps for Northbrook, IL
Test your own tap with a certified lab first-draw sample; Northbrook, IL may offer free or low-cost kits through the utility. If your own line is lead, replacing the private side runs about $1,200-$12,300 (EPA average about $4,700). Ask Northbrook whether it covers that cost before hiring anyone - many utilities now do.
These figures describe homes the utility sampled, not your tap. Only your service line record or a test of your own water answers the question for your house. The lead result guide covers how utilities pick the homes they sample. See what changes at 10 ppb in 2027.