Willowbrook, IL
Lead reported as not detected
Latest 90th-percentile lead: reported as 0 (not detected) (monitoring period 2025-2025). The federal action level is 15 ppb today and drops to 10 ppb in Nov 2027; EPA's health goal is 0. The latest 90th-percentile result was reported as 0 (not detected at the lab's limit). That says the sampled homes were low, not that your home has no lead service line. Check your utility's service line inventory for your address.
Willowbrook at a glance
Willowbrook serves about 9,000 people through 2,207 service connections, which makes it a medium-sized system under EPA's size classes. It is owned by a local government (city, town, county or district) and draws surface water, in Dupage County, Illinois. EPA system ID: IL0431100; phone on file: 630-323-8215. Ask them for your address in their service line inventory - every system had to publish one by Oct 2024.
Every lead result on file
Against the period ending 2025 (0 ppb) the latest result is about the same. The highest 90th-percentile result EPA holds for Willowbrook is 2.3 ppb across 5 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2025 | 0 (not detected) |
| 2025 | 0 (not detected) |
| 2023 | 1.3 ppb |
| 2020 | 2.3 ppb |
| 2017 | 2.1 ppb |
How Willowbrook 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. Willowbrook's reported as 0 (not detected) sits at the 51st percentile in Illinois and the 37th nationally (higher means more lead). Systems reporting 0 tie at the bottom, so the rank mostly reflects size among them.
Other water systems in Dupage County
47 other systems share Dupage County; 26 of them have a higher latest lead result than Willowbrook. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Naperville | 156,406 | 6.1 ppb |
| Wheaton | 53,970 | 2.32 ppb |
| Downers Grove | 49,425 | 4.98 ppb |
| Elmhurst | 45,000 | 5.52 ppb |
| Lombard | 44,476 | 10.6 ppb |
| Carol Stream | 39,854 | 1.05 ppb |
| Addison | 38,017 | 2 ppb |
| Woodridge | 33,566 | 0 (not detected) |
| Glendale Heights | 33,176 | 0 (not detected) |
| Glen Ellyn | 28,500 | 1.87 ppb |
Your move
Look up your address in Willowbrook's service line inventory. If it says lead, galvanized or unknown, test your tap. If your own line is lead, replacing the private side runs about $1,200-$12,300 (EPA average about $4,700). Ask Willowbrook 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. A zero today does not rule out a jump later - the rules are tightening in 2027.