B78/100
Darien Tap Water Quality: Is It Safe to Drink? (2026 Report)
Serving 33,976 residents · Illinois
What's In Darien's Tap Water?
69
Contaminants Tested
0
Exceed EPA Limits
0
Above EPA Goals
EPA Violation History
1
Violation (last 5yr)
0
Unresolved
0
Health-Related
TIER 3Resolved
Surface water treatment technique failure
When: July 1, 2024 – July 18, 2024Enforcement: Resolving — corrective action underway
Understanding violation severity
Tier 1Urgent health risk. Utility must notify all customers within 24 hours.Tier 2Important health or treatment issue. Customers notified within 30 days.Tier 3Administrative or monitoring issue. Reported in the annual water quality report.
Source: EPA Safe Drinking Water Information System (SDWIS) · Updated quarterly
Water Utility Details
YORK TOWNSHIP WATER SYSTEM
Population Served
1,423
Water Source
Purchased Surface Water
System ID
IL0430010
SOUTHEAST REGIONAL WATER FACILITY
Population Served
6,940
Water Source
Purchased Surface Water
System ID
IL0430060
DARIEN
Population Served
21,751
Water Source
Purchased Surface Water
System ID
IL0430270
GLEN ELLYN HEIGHTS SUBDIVISION
Population Served
1,931
Water Source
Purchased Surface Water
System ID
IL0435500
STEEPLE RUN SBDV
Population Served
1,931
Water Source
Purchased Surface Water
System ID
IL0437160
Frequently Asked Questions About Darien Water
Is Darien tap water safe to drink?
Darien, Illinois tap water receives a grade of B (78/100), which is considered good. Out of 69 contaminants tested, none exceed EPA maximum contaminant levels (MCLs) and 1 exceed health guidelines (MCLGs). While the water meets federal standards, some residents may still choose to use a filter for additional peace of mind.
What contaminants are in Darien's water?
Of the 69 contaminants tested in Darien's water supply, the most notable include Lead (90th percentile). No contaminants exceed EPA legal limits. 1 contaminant(s) exceed EPA health goals (MCLGs), which are non-enforceable targets set at levels with no known health risk.
Does Darien have any water quality violations?
Yes, Darien has 71 EPA violation(s) on record, with the most recent in 2025. Violation types include Other, MR, TT. 8 of these are health-based violations, which are the most serious category.
Do I need a water filter in Darien?
Darien water meets EPA standards, so a filter is not strictly necessary. However, some residents prefer the added security of a water filter. EPA health goals (MCLGs) are stricter than legal limits and are set at levels with zero expected health risk. 1 contaminant(s) exceed these stricter goals.
Where does Darien's tap water come from?
Darien's drinking water is sourced from purchased surface water and supplied by YORK TOWNSHIP WATER SYSTEM and 4 other water system(s). The system serves approximately 33,976 people. Surface water sources include rivers, lakes, and reservoirs.
How often is Darien's water tested?
Under the Safe Drinking Water Act (SDWA), water utilities are required to regularly test for over 90 contaminants. Testing frequency varies by contaminant — some are tested monthly, others quarterly or annually. Darien's water systems must report results to the EPA and publish an annual Consumer Confidence Report (CCR). The data on this page reflects the latest available EPA testing data.
How does Darien's water compare to other cities in Illinois?
Darien's water quality score of 78/100 earns a grade of B, which is considered good. This is an above-average score compared to many cities nationwide. Visit our Illinois state page to see how all cities in the state compare.
What should I do if I'm concerned about Darien's water quality?
If you have concerns about Darien's tap water, consider these steps: (1) Request your utility's annual Consumer Confidence Report for detailed local data. (2) Get your water independently tested through a state-certified laboratory. (3) Consider an NSF-certified water filter rated for the contaminants found in your area. (4) Contact your water utility (YORK TOWNSHIP WATER SYSTEM) with specific questions. (5) Report water quality issues to your state drinking water program or the EPA Safe Drinking Water Hotline at 800-426-4791.