Mercer County Water Quality: 3 Cities Ranked by the Records
Mercer County, New Jersey: 3 city reports built from EPA and utility records. A county has many suppliers; each city shows the system that serves it.
Highest result for each contaminant
One row per contaminant: the highest result any system in the county reported, against its limit. Open a row for the systems behind it.
Perfluorooctanoic acid (PFOA)Detected in 1 system of 3 tested4.0 ng/L federal MCL (2024) · US EPAHighest11.6 ng/L
- AQUA NJ - HAMILTON SQUARE11.6 ng/LSample date: 2025-03-25 to 2025-09-03
- EAST WINDSOR MUANot detected · below 4.0 ng/L lab reporting limitSample date: 2024-02-14 to 2024-09-17
- TRENTON WATER WORKSNot detected · below 4.0 ng/L lab reporting limitSample date: 2023-04-19 to 2024-01-22
Perfluorooctanesulfonic acid (PFOS)Detected in 1 system of 3 tested4.0 ng/L federal MCL (2024) · US EPAHighest11.4 ng/L
- AQUA NJ - HAMILTON SQUARE11.4 ng/LSample date: 2025-03-25 to 2025-09-03
- EAST WINDSOR MUANot detected · below 4.0 ng/L lab reporting limitSample date: 2024-02-14 to 2024-09-17
- TRENTON WATER WORKSNot detected · below 4.0 ng/L lab reporting limitSample date: 2023-04-19 to 2024-01-22
LithiumDetected in 2 systems of 3 tested10 µg/L EPA health reference level (screening, not a legal limit) · US EPAHighest27.5 µg/L
- AQUA NJ - HAMILTON SQUARE27.5 µg/LSample date: 2025-03-25 to 2025-09-03
- EAST WINDSOR MUA25.1 µg/LSample date: 2024-02-14 to 2024-09-17
- TRENTON WATER WORKSNot detected · below 9.0 µg/L lab reporting limitSample date: 2023-04-19 to 2024-01-22
Perfluorohexanesulfonic acid (PFHxS)Detected in 1 system of 3 tested10 ng/L federal MCL (2024) · US EPAHighest10.4 ng/L
- AQUA NJ - HAMILTON SQUARE10.4 ng/LSample date: 2025-03-25 to 2025-09-03
- EAST WINDSOR MUANot detected · below 3.0 ng/L lab reporting limitSample date: 2024-02-14 to 2024-09-17
- TRENTON WATER WORKSNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-04-19 to 2024-01-22
Lead (90th percentile)Detected in 2 systems of 3 tested15 µg/L federal action level · US EPAHighest6 µg/L
- TRENTON WATER WORKS6 µg/LMonitoring period: 2026–2026 (still open)
- EAST WINDSOR MUA1.61 µg/LMonitoring period: 2022–2024
- AQUA NJ - HAMILTON SQUARENot detectedMonitoring period: 2024–2026 (still open)
Perfluorohexanoic acid (PFHxA)Detected in 1 system of 3 tested400,000 ng/L Michigan EGLE state MCL (strictest US state) · Michigan EGLEHighest5.4 ng/L
- AQUA NJ - HAMILTON SQUARE5.4 ng/LSample date: 2025-03-25 to 2025-09-03
- EAST WINDSOR MUANot detected · below 3.0 ng/L lab reporting limitSample date: 2024-02-14 to 2024-09-17
- TRENTON WATER WORKSNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-04-19 to 2024-01-22
Water hardnessDetected in 1 systemAesthetic, no federal health limit · USGSHighest6.3 gpg
- TRENTON WATER WORKS6.3 gpgReporting year: 2025
Perfluoroheptanoic acid (PFHpA)Detected in 1 system of 3 testedNo federal or state limit; shown for transparencyHighest3.4 ng/L
- AQUA NJ - HAMILTON SQUARE3.4 ng/LSample date: 2025-03-25 to 2025-09-03
- EAST WINDSOR MUANot detected · below 3.0 ng/L lab reporting limitSample date: 2024-02-14 to 2024-09-17
- TRENTON WATER WORKSNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-04-19 to 2024-01-22
1 more contaminant detectedShow
Perfluoropentanoic acid (PFPeA)Detected in 1 system of 3 testedNo federal or state limit; shown for transparencyHighest4.6 ng/L
- AQUA NJ - HAMILTON SQUARE4.6 ng/LSample date: 2025-03-25 to 2025-09-03
- EAST WINDSOR MUANot detected · below 3.0 ng/L lab reporting limitSample date: 2024-02-14 to 2024-09-17
- TRENTON WATER WORKSNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-04-19 to 2024-01-22
23 PFAS tested, none detected in any systemShow
Tested in these 3 systems: AQUA NJ - HAMILTON SQUARE, EAST WINDSOR MUA, TRENTON WATER WORKS
- 11-Chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS)
- 1H, 1H, 2H, 2H-perfluorodecane sulfonic acid (8:2 FTS)
- 1H, 1H, 2H, 2H-perfluorohexane sulfonic acid (4:2 FTS)
- 1H, 1H, 2H, 2H-perfluorooctane sulfonic acid (6:2 FTS)
- 4,8-Dioxa-3H-perfluorononanoic acid (ADONA)
- 9-Chlorohexadecafluoro-3-oxanone-1-sulfonic acid (9Cl-PF3ONS)
- Hexafluoropropylene oxide dimer acid (HFPO-DA) (GenX chemicals)
- N-ethyl perfluorooctanesulfonamidoacetic acid (NEtFOSAA)
- N-methyl perfluorooctanesulfonamidoacetic acid (NMeFOSAA)
- Nonafluoro-3,6-dioxaheptanoic acid (NFDHA)
- Perfluoro (2-ethoxyethane) sulfonic acid (PFEESA)
- Perfluoro-3-methoxypropanoic acid (PFMPA)
- Perfluoro-4-methoxybutanoic acid (PFMBA)
- Perfluorobutanesulfonic acid (PFBS)
- Perfluorobutanoic acid (PFBA)
- Perfluorodecanoic acid (PFDA)
- Perfluorododecanoic acid (PFDoA)
- Perfluoroheptanesulfonic acid (PFHpS)
- Perfluorononanoic acid (PFNA)
- Perfluoropentanesulfonic acid (PFPeS)
- Perfluorotetradecanoic acid (PFTA)
- Perfluorotridecanoic acid (PFTrDA)
- Perfluoroundecanoic acid (PFUnA)
Cities ranked by the records
Ranked by the Purity Score of each city's main water system, highest first. Scores belong to water systems; there is no county score. The score is computed only from contaminants measured in the published EPA record, so this ranks the record, not which city's water is safest. How the score works.
0of 3 cities above the 15 µg/L action level
Based on each system's 90th-percentile result. Lead from household plumbing isn't in this record.
Lead in New Jersey1city reports hardness · Trenton, 6.3 gpg
None above 7 gpg, the USGS threshold for hard water. An aesthetic measure with no federal health limit.
Hard water explainedLargest water systems
- TrentonTRENTON WATER WORKS · NJ1111001217,000 served
- Hamilton SquareAQUA NJ - HAMILTON SQUARE · NJ110300139,128 served
- WindsorEAST WINDSOR MUA · NJ110100225,000 served
Frequently asked
How does Mercer County tap water compare across cities?
PurityMap ranks 3 cities in Mercer County by the Purity Score of each city's main water system, computed only from contaminants measured in the published EPA record. Scores belong to water systems, not to cities. The highest published score is Windsor's main water system: EAST WINDSOR MUA · PWSID NJ1101002 · Purity Score 95 (Excellent) · Confidence: moderate · Assessed at the water-system level. The ranking compares the records, not which city's water is safest, and your own tap can differ with household plumbing.
How many Mercer County cities had a PFAS sample above a 2024 EPA limit?
1 of 3 Mercer County city reports had a PFAS sample above a 2024 EPA limit in EPA's UCMR 5 testing, including Hamilton Square (PFOA 11.6 ng/L). That limit is judged on a yearly average, and water systems have until 2029 to meet it, so a single sample is not a violation. PFAS were detected at any level in 1.
Is there lead in Mercer County tap water?
Utilities report lead as a 90th-percentile result from home taps. 2 of 3 Mercer County cities reported a value above zero, and none was above the 15 µg/L federal action level. Lead usually comes from a building's own pipes and fixtures, so only a test at your tap tells you what you drink.
Have Mercer County water systems had drinking-water violations?
1 city in Mercer County has a health-based violation in the federal SDWIS record within about the last ten years. Each city report lists the contaminant, year and whether it was resolved.
Does Mercer County have hard water?
Hardness is published in utility water-quality reports for 1 Mercer County city on record; the hardest is Trenton at 6.3 grains per gallon. Hardness affects scale and appliances; it is not a health finding.
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