Mount Prospect, IL
Lead detected, under the action levels
Latest 90th-percentile lead: 2.22 ppb (monitoring period 2026-2028). The federal action level is 15 ppb today and drops to 10 ppb in Nov 2027; EPA's health goal is 0. Lead was measured in sampled homes but the 90th percentile is under both action levels. EPA's health goal for lead is zero, so test your own tap if your home was built before 1986 or anyone in it is pregnant or a young child.
About Mount Prospect
Mount Prospect serves about 41,000 people through 11,590 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: IL0311980; phone on file: 847-870-5640. Call that number and ask whether your address has a lead, galvanized or unknown service line.
Lead results over time
That is up 2.22 ppb from 0 ppb in the period ending 2025. The highest 90th-percentile result EPA holds for Mount Prospect is 4.27 ppb across 8 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2028 | 2.22 ppb |
| 2025 | 0 (not detected) |
| 2025 | 1.8 ppb |
| 2025 | 4.27 ppb |
| 2025 | 4.11 ppb |
| 2023 | 2.82 ppb |
| 2020 | 3.79 ppb |
| 2017 | 3.88 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. Mount Prospect's 2.22 ppb sits at the 75th percentile in Illinois and the 75th nationally (higher means more lead).
Neighbouring systems
154 other systems share Cook County; 76 of them have a higher latest lead result than Mount Prospect. 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 Mount Prospect, IL
Test your own tap with a certified lab first-draw sample; Mount Prospect, 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 Mount Prospect 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. Systems that went over once often dip back under; here is what that means.