Tap Water Safety Report for Oswego, Illinois
Oswego, Illinois tap water scored 51/100 (D) based on EPA data. Multiple contaminants are at concerning levels. A water filter is recommended, especially for children and pregnant women.
Overall Score
51/100
Grade: D
Contaminants Tested
10
All within limits
EPA Violations
2
All resolved
Water Source
mixed
Mixed sources
Population Served
32,956
residents
Water Systems
1
serving this area
2 contaminant(s) are approaching EPA limits and should be monitored.
Detected level
0.0092 mg/L
61% of EPA limit
Health effects: Developmental delays in children, kidney damage, and high blood pressure in adults. No safe level of lead exposure exists.
Detected level
45.2996 ug/L
57% of EPA limit
Health effects: Disinfection byproducts linked to increased risk of bladder cancer and reproductive issues with long-term exposure.
Based on Oswego's water quality data, here are our specific recommendations:
Oswego's water has multiple contaminants at concerning levels. An under-sink reverse osmosis system or a certified multi-stage filter is strongly recommended for drinking and cooking water.
If lead is a concern, run cold water for 1-2 minutes each morning before drinking. Never use hot tap water for cooking or baby formula, as heat increases lead leaching from pipes.
Babies and young children are especially vulnerable to water contaminants. Use filtered or bottled water for mixing formula and for drinking water until filtration is installed.
How contaminant levels compare to EPA limits (50% of overall score)
EPA violation history and enforcement actions (30% of overall score)
Water system infrastructure and source quality (20% of overall score)
With a score of 51/100, Oswego's tap water has significant quality concerns. We strongly recommend against using unfiltered tap water for babies or young children. Use bottled water or invest in a reverse osmosis filter for any water consumed by children. Infants are especially vulnerable to contaminants like lead and nitrates, which can cause serious developmental and health issues.
Oswego's water has been tested for 10 contaminants. None currently exceed EPA maximum contaminant levels. The most notable detections include: Lead (0.0092 mg/L, EPA limit: 0.015 mg/L — 61% of limit); Total Trihalomethanes (45.2996 ug/L, EPA limit: 80 ug/L — 57% of limit); Mercury (0.001 mg/L, EPA limit: 0.002 mg/L — 49% of limit); Nitrite (0.4547 mg/L, EPA limit: 1 mg/L — 46% of limit); Arsenic (0.0043 mg/L, EPA limit: 0.01 mg/L — 43% of limit). The water system has no active EPA violations. Water quality can vary seasonally and by neighborhood, so home testing provides the most accurate picture for your specific tap.
Absolutely. With a water quality score of 51/100, filtering is strongly recommended in Oswego. A reverse osmosis (RO) system is the most effective option, removing up to 99% of contaminants. At minimum, use a certified pitcher filter rated for the specific contaminants found in your water. Multiple contaminants at concerning levels make filtration an important health measure.
Oswego's water quality score of 51/100 (D) is 21 points below the national average of 72. The city's water comes from a mix of groundwater and surface water sources. This indicates significant water quality challenges that the city should work to address. You can see how Oswego compares to nearby cities in our state rankings.
Detailed contaminant data, violation history, and water system information for Oswego.
Find the best water filter for Oswego based on detected contaminants and your budget.
See how Oswego compares to other cities across Illinois.
See how Oswego ranks among all cities in the US for water quality.
Data Disclaimer
This report is based on publicly available EPA data and water quality test results. Water quality can vary by neighborhood, building age, and season. This information is for educational purposes and should not replace professional water testing. If you have specific health concerns about your water, contact your local water utility or a certified water testing laboratory. Last data update: February 2, 2026.