Delaware County Water Quality: 2 Cities Ranked by the Records
Delaware County, Pennsylvania: 2 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 2 systems4.0 ng/L federal MCL (2024) · US EPAHighest12.6 ng/L
- AQUA PA MAIN SYSTEM12.6 ng/LSample date: 2024-02-01 to 2024-12-11
- CHESTER WATER AUTHORITY5.1 ng/LSample date: 2024-02-12 to 2024-11-13
Perfluorooctanesulfonic acid (PFOS)Detected in 1 system of 2 tested4.0 ng/L federal MCL (2024) · US EPAHighest9.2 ng/L
- AQUA PA MAIN SYSTEM9.2 ng/LSample date: 2024-02-01 to 2024-12-11
- CHESTER WATER AUTHORITYNot detected · below 4.0 ng/L lab reporting limitSample date: 2024-02-12 to 2024-11-13
LithiumDetected in 1 system of 2 tested10 µg/L EPA health reference level (screening, not a legal limit) · US EPAHighest15.7 µg/L
- AQUA PA MAIN SYSTEM15.7 µg/LSample date: 2024-02-01 to 2024-12-11
- CHESTER WATER AUTHORITYNot detected · below 9.0 µg/L lab reporting limitSample date: 2024-02-12 to 2024-11-13
Perfluorononanoic acid (PFNA)Detected in 1 system of 2 tested10 ng/L federal MCL (2024) · US EPAHighest12 ng/L
- AQUA PA MAIN SYSTEM12 ng/LSample date: 2024-02-01 to 2024-12-11
- CHESTER WATER AUTHORITYNot detected · below 4.0 ng/L lab reporting limitSample date: 2024-02-12 to 2024-11-13
Water hardnessDetected in 1 systemAesthetic, no federal health limit · USGSHighest7 gpg
- CHESTER WATER AUTHORITY7 gpgReporting year: 2025
Perfluorohexanesulfonic acid (PFHxS)Detected in 1 system of 2 tested10 ng/L federal MCL (2024) · US EPAHighest7.7 ng/L
- AQUA PA MAIN SYSTEM7.7 ng/LSample date: 2024-02-01 to 2024-12-11
- CHESTER WATER AUTHORITYNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-02-12 to 2024-11-13
Lead (90th percentile)Detected in 1 system of 2 tested15 µg/L federal action level · US EPAHighest4.76 µg/L
- CHESTER WATER AUTHORITY4.76 µg/LMonitoring period: 2025–2025
- AQUA PA MAIN SYSTEMNot detectedMonitoring period: 2025–2025
Perfluorobutanesulfonic acid (PFBS)Detected in 2 systems2,000 ng/L EPA health advisory (screening, not a legal limit) · US EPAHighest9.5 ng/L
- AQUA PA MAIN SYSTEM9.5 ng/LSample date: 2024-02-01 to 2024-12-11
- CHESTER WATER AUTHORITY4.5 ng/LSample date: 2024-02-12 to 2024-11-13
4 more contaminants detectedShow
Perfluorohexanoic acid (PFHxA)Detected in 2 systems400,000 ng/L Michigan EGLE state MCL (strictest US state) · Michigan EGLEHighest17.2 ng/L
- AQUA PA MAIN SYSTEM17.2 ng/LSample date: 2024-02-01 to 2024-12-11
- CHESTER WATER AUTHORITY3.9 ng/LSample date: 2024-02-12 to 2024-11-13
Perfluorobutanoic acid (PFBA)Detected in 1 system of 2 testedNo federal or state limit; shown for transparencyHighest10.1 ng/L
- AQUA PA MAIN SYSTEM10.1 ng/LSample date: 2024-02-01 to 2024-12-11
- CHESTER WATER AUTHORITYNot detected · below 5.0 ng/L lab reporting limitSample date: 2024-02-12 to 2024-11-13
Perfluoroheptanoic acid (PFHpA)Detected in 1 system of 2 testedNo federal or state limit; shown for transparencyHighest6.9 ng/L
- AQUA PA MAIN SYSTEM6.9 ng/LSample date: 2024-02-01 to 2024-12-11
- CHESTER WATER AUTHORITYNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-02-12 to 2024-11-13
Perfluoropentanoic acid (PFPeA)Detected in 2 systemsNo federal or state limit; shown for transparencyHighest21.8 ng/L
- AQUA PA MAIN SYSTEM21.8 ng/LSample date: 2024-02-01 to 2024-12-11
- CHESTER WATER AUTHORITY4.1 ng/LSample date: 2024-02-12 to 2024-11-13
20 PFAS tested, none detected in any systemShow
Tested in these 2 systems: AQUA PA MAIN SYSTEM, CHESTER WATER AUTHORITY
- 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)
- Perfluorodecanoic acid (PFDA)
- Perfluorododecanoic acid (PFDoA)
- Perfluoroheptanesulfonic acid (PFHpS)
- 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 2 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 Pennsylvania1city reports hardness · Chester, 7 gpg
None above 7 gpg, the USGS threshold for hard water. An aesthetic measure with no federal health limit.
Hard water explainedLargest water systems
- Drexel HillAQUA PA MAIN SYSTEM · PA1460073822,600 served
- ChesterCHESTER WATER AUTHORITY · PA1230004140,437 served
Frequently asked
How does Delaware County tap water compare across cities?
PurityMap ranks 2 cities in Delaware 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 Chester's main water system: CHESTER WATER AUTHORITY · PWSID PA1230004 · Purity Score 67 (Fair) · 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 Delaware County cities had a PFAS sample above a 2024 EPA limit?
2 of 2 Delaware County city reports had a PFAS sample above a 2024 EPA limit in EPA's UCMR 5 testing, including Drexel Hill (PFOA 12.6 ng/L), Chester (PFOA 5.1 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 2.
Is there lead in Delaware County tap water?
Utilities report lead as a 90th-percentile result from home taps. 1 of 2 Delaware 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 Delaware County water systems had drinking-water violations?
1 city in Delaware 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 Delaware County have hard water?
Hardness is published in utility water-quality reports for 1 Delaware County city on record; the hardest is Chester at 7 grains per gallon. Hardness affects scale and appliances; it is not a health finding.
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