Oswego water quality report, rewritten
- Serves
- 38,169
- Connections
- 12,887
- Water source
- Groundwater
- Based in
- Oswego, IL
- County
- Kendall
- Owner
- Local government
The ZIP code it serves
PWSID IL09301502026 edition · EPA data
Read this first
- Lithium (above EPA’s health benchmark) was found in 16 of 16 samples, highest 114 ppb. Above EPA’s health reference level of 10 ppb, a screening level rather than an enforceable limit.
1 health-based violation since 2016. Details are below.
What was found
Highlighted: above the health goal, or EPA’s health benchmark where there is no goal. Circled: above the legal limit in at least one sample, or the action level. Every scale puts that line at its middle.
Lithium (above EPA’s health benchmark)
Comes from the source
114ppb
Highest of 16 samples; found in 16
Above EPA’s health reference level of 10 ppb, a screening level rather than an enforceable limit.
What handles it
No certification claim covers this compound yet.
EPA UCMR 5, samples taken from Aug. 28, 2024 to Feb. 14, 2025. Each blue tick is one sample where it was found.
Tested and not found
Below EPA’s minimum reporting level in every sample taken from Aug. 28, 2024 to Feb. 14, 2025. Not found means not measured above that level, which is not the same as zero.
All 30 compounds tested and not found
- 11Cl-PF3OUdS
- 4:2 FTS
- 6:2 FTS
- 8:2 FTS
- 9Cl-PF3ONS
- ADONA
- HFPO-DA (GenX)
- Lead
- NEtFOSAA
- NFDHA
- NMeFOSAA
- PFBA
- PFBS
- PFDA
- PFDoA
- PFEESA
- PFHpA
- PFHpS
- PFHxA
- PFHxS
- PFMBA
- PFMPA
- PFNA
- PFOA
- PFOS
- PFPeA
- PFPeS
- PFTA
- PFTrDA
- PFUnA
Violations since 2016
| Contaminant or rule | Type | Period | Measured | Status |
|---|---|---|---|---|
| Combined Radium (-226 and -228) | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2017 to March 31, 2017 | 6.0 PCI/L | Resolved |
| Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 5 monitoring or reporting violations not shown. | ||||
What this report cannot tell you
- Levels of everything else. Federal bulk data carries results for PFAS, lithium, lead and copper, and violations for the rest. Nitrate, arsenic, disinfection byproducts and other levels are in Oswego’s own annual report, which it must send you every year.
- Your own plumbing. Lead results are the 90th percentile across homes the utility samples. Your home’s service line, solder and fixtures decide yours. A certified lab test is the only way to know.
- Anything after the latest data. SDWIS data is from 2026 Q2; UCMR 5 samples are from Aug. 28, 2024 to Feb. 14, 2025.
What to do next
Read up on Lithium
What each one does to health, where it comes from, and the certification claim that addresses it.
About LithiumGet the utility’s own report
Oswego must send you a water quality report every year. It lists nitrate, arsenic and byproduct levels this page cannot.
How to read itTest your own tap for lead
Your service line, solder and fixtures decide the lead at your faucet, not the utility’s average.
Lead in your water: what to doDecide if you want a filter at all
A filter for taste or chlorine is a preference, not a need. The standards say what each kind can do.
NSF/ANSI standards, decoded
Other Illinois utilities
- Chicago2.7 million
- Aurora183,000
- Joliet160,000
- Naperville156,406
- IL American - Champaign150,000
- Rockford147,051
- IL American - Peoria137,575
- IL American - East St Louis131,368
- Springfield117,444
- Elgin114,797
- Waukegan87,149
- Cicero83,000
Sources
- EPA UCMR 5 occurrence data, file of Aug. 27, 2026
- EPA SDWA bulk download (SDWIS federal data), 2026 Q2
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.