Grayslake, 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.
Grayslake at a glance
Grayslake serves about 21,248 people through 7,298 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 Lake County, Illinois. EPA system ID: IL0970250; phone on file: 847-223-8515. They can tell you what your service line is made of and whether they pay to replace it.
Grayslake's lead record
Against the period ending 2025 (12 ppb) the latest result is about the same. The highest 90th-percentile result EPA holds for Grayslake is 12 ppb across 7 monitoring periods, none of them over 15 ppb (2 over 10 ppb).
| Period ending | 90th-percentile lead |
|---|---|
| 2026 | 11 ppb over 10 |
| 2025 | 12 ppb over 10 |
| 2025 | 2 ppb |
| 2025 | 10 ppb |
| 2022 | 7 ppb |
| 2019 | 7.6 ppb |
| 2016 | 6 ppb |
Against other Illinois systems
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. Grayslake's 11 ppb sits at the 97th percentile in Illinois and the 98th nationally (higher means more lead).
Nearby utilities
103 other systems share Lake County; 7 of them have a higher latest lead result than Grayslake. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Waukegan | 87,149 | 10 ppb |
| Vernon Hills - Lake Co Pw | 33,207 | 0 (not detected) |
| Mundelein | 31,500 | 4.3 ppb |
| Gurnee | 30,193 | 0.3 ppb |
| Highland Park | 30,176 | 0 (not detected) |
| Round Lake Beach | 27,200 | 0 (not detected) |
| Zion | 24,442 | 11.2 ppb |
| Great Lakes Naval Training Station | 23,000 | 0 (not detected) |
| Libertyville | 20,500 | 5.61 ppb |
| Lake Zurich | 19,759 | 4.67 ppb |
What to do in your house
Test your own tap with a certified lab first-draw sample; Grayslake, 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 Grayslake 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. This system is in the band the 2027 10 ppb rule changes.