McHenry County Water Quality: 7 Cities Ranked by the Records
McHenry County, Illinois: 7 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.
Copper (90th percentile)Detected in 3 systems1.3 mg/L federal action level · US EPAHighest1.6 mg/L
- ALGONQUIN1.6 mg/LMonitoring period: 2022–2024
- WOODSTOCK1.5 mg/LMonitoring period: 2021–2023
- LAKE IN THE HILLS1.4 mg/LMonitoring period: 2025–2025
LithiumDetected in 2 systems of 7 tested10 µg/L EPA health reference level (screening, not a legal limit) · US EPAHighest10.8 µg/L
- LAKE IN THE HILLS10.8 µg/LSample date: 2024-10-15 to 2025-04-09
- MCHENRY9.09 µg/LSample date: 2023-05-23 to 2023-10-16
- ALGONQUINNot detected · below 9.0 µg/L lab reporting limitSample date: 2024-05-15 to 2024-11-04
- CARYNot detected · below 9.0 µg/L lab reporting limitSample date: 2024-05-29 to 2024-11-13
- CRYSTAL LAKENot detected · below 9.0 µg/L lab reporting limitSample date: 2024-12-03 to 2025-09-09
- HUNTLEYNot detected · below 9.0 µg/L lab reporting limitSample date: 2024-04-30 to 2024-10-10
- WOODSTOCKNot detected · below 9.0 µg/L lab reporting limitSample date: 2023-04-18 to 2023-10-09
Lead (90th percentile)Detected in 6 systems of 7 tested15 µg/L federal action level · US EPAHighest7 µg/L
- WOODSTOCK7 µg/LMonitoring period: 2025–2025
- CRYSTAL LAKE6.8 µg/LMonitoring period: 2026–2026 (still open)
- MCHENRY6.7 µg/LMonitoring period: 2026–2026 (still open)
- ALGONQUIN1.96 µg/LMonitoring period: 2026–2028 (still open)
- CARY1.7 µg/LMonitoring period: 2026–2028 (still open)
- HUNTLEY1.1 µg/LMonitoring period: 2026–2028 (still open)
- LAKE IN THE HILLSNot detectedMonitoring period: 2025–2025
Perfluorobutanesulfonic acid (PFBS)Detected in 2 systems of 7 tested2,000 ng/L EPA health advisory (screening, not a legal limit) · US EPAHighest4.6 ng/L
- CRYSTAL LAKE4.6 ng/LSample date: 2024-12-03 to 2025-11-03
- MCHENRY3.9 ng/LSample date: 2023-05-23 to 2024-11-05
- ALGONQUINNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-05-15 to 2024-11-04
- CARYNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-05-29 to 2024-11-13
- HUNTLEYNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-04-30 to 2024-10-10
- LAKE IN THE HILLSNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-10-15 to 2025-04-09
- WOODSTOCKNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-04-18 to 2023-11-06
Perfluorohexanoic acid (PFHxA)Detected in 1 system of 7 tested400,000 ng/L Michigan EGLE state MCL (strictest US state) · Michigan EGLEHighest6.9 ng/L
- CARY6.9 ng/LSample date: 2024-05-29 to 2024-11-13
- ALGONQUINNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-05-15 to 2024-11-04
- CRYSTAL LAKENot detected · below 3.0 ng/L lab reporting limitSample date: 2024-12-03 to 2025-11-03
- HUNTLEYNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-04-30 to 2024-10-10
- LAKE IN THE HILLSNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-10-15 to 2025-04-09
- MCHENRYNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-05-23 to 2024-11-05
- WOODSTOCKNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-04-18 to 2023-11-06
1H, 1H, 2H, 2H-perfluorooctane sulfonic acid (6:2 FTS)Detected in 1 system of 7 testedNo federal or state limit; shown for transparencyHighest5.7 ng/L
- CARY5.7 ng/LSample date: 2024-05-29 to 2024-11-13
- ALGONQUINNot detected · below 5.0 ng/L lab reporting limitSample date: 2024-05-15 to 2024-11-04
- CRYSTAL LAKENot detected · below 5.0 ng/L lab reporting limitSample date: 2024-12-03 to 2025-11-03
- HUNTLEYNot detected · below 5.0 ng/L lab reporting limitSample date: 2024-04-30 to 2024-10-10
- LAKE IN THE HILLSNot detected · below 5.0 ng/L lab reporting limitSample date: 2024-10-15 to 2025-04-09
- MCHENRYNot detected · below 5.0 ng/L lab reporting limitSample date: 2023-05-23 to 2024-11-05
- WOODSTOCKNot detected · below 5.0 ng/L lab reporting limitSample date: 2023-04-18 to 2023-11-06
Perfluorobutanoic acid (PFBA)Detected in 1 system of 7 testedNo federal or state limit; shown for transparencyHighest7.4 ng/L
- CARY7.4 ng/LSample date: 2024-05-29 to 2024-11-13
- ALGONQUINNot detected · below 5.0 ng/L lab reporting limitSample date: 2024-05-15 to 2024-11-04
- CRYSTAL LAKENot detected · below 5.0 ng/L lab reporting limitSample date: 2024-12-03 to 2025-11-03
- HUNTLEYNot detected · below 5.0 ng/L lab reporting limitSample date: 2024-04-30 to 2024-10-10
- LAKE IN THE HILLSNot detected · below 5.0 ng/L lab reporting limitSample date: 2024-10-15 to 2025-04-09
- MCHENRYNot detected · below 5.0 ng/L lab reporting limitSample date: 2023-05-23 to 2024-11-05
- WOODSTOCKNot detected · below 5.0 ng/L lab reporting limitSample date: 2023-04-18 to 2023-11-06
Perfluoroheptanoic acid (PFHpA)Detected in 1 system of 7 testedNo federal or state limit; shown for transparencyHighest4 ng/L
- CARY4 ng/LSample date: 2024-05-29 to 2024-11-13
- ALGONQUINNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-05-15 to 2024-11-04
- CRYSTAL LAKENot detected · below 3.0 ng/L lab reporting limitSample date: 2024-12-03 to 2025-11-03
- HUNTLEYNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-04-30 to 2024-10-10
- LAKE IN THE HILLSNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-10-15 to 2025-04-09
- MCHENRYNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-05-23 to 2024-11-05
- WOODSTOCKNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-04-18 to 2023-11-06
1 more contaminant detectedShow
Perfluoropentanoic acid (PFPeA)Detected in 2 systems of 7 testedNo federal or state limit; shown for transparencyHighest12 ng/L
- CARY12 ng/LSample date: 2024-05-29 to 2024-11-13
- CRYSTAL LAKE4.5 ng/LSample date: 2024-12-03 to 2025-11-03
- ALGONQUINNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-05-15 to 2024-11-04
- HUNTLEYNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-04-30 to 2024-10-10
- LAKE IN THE HILLSNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-10-15 to 2025-04-09
- MCHENRYNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-05-23 to 2024-11-05
- WOODSTOCKNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-04-18 to 2023-11-06
23 PFAS tested, none detected in any systemShow
Tested in these 7 systems: ALGONQUIN, CARY, CRYSTAL LAKE, HUNTLEY, LAKE IN THE HILLS, MCHENRY, WOODSTOCK
- 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)
- 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)
- Perfluorohexanesulfonic acid (PFHxS)
- Perfluorononanoic acid (PFNA)
- Perfluorooctanesulfonic acid (PFOS)
- Perfluorooctanoic acid (PFOA)
- Perfluoropentanesulfonic acid (PFPeS)
- Perfluorotetradecanoic acid (PFTA)
- Perfluorotridecanoic acid (PFTrDA)
- Perfluoroundecanoic acid (PFUnA)
Cities ranked by the records
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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 7 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 IllinoisLargest water systems
- Crystal LakeCRYSTAL LAKE · IL111015040,661 served
- AlgonquinALGONQUIN · IL111005030,700 served
- Lake In The HillsLAKE IN THE HILLS · IL111040028,661 served
- HuntleyHUNTLEY · IL111035028,495 served
- WoodstockWOODSTOCK · IL111095025,630 served
- McHenryMCHENRY · IL111060022,335 served
- CaryCARY · IL111010017,826 served
Frequently asked
How does McHenry County tap water compare across cities?
PurityMap ranks 7 cities in McHenry 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 Cary's main water system: CARY · PWSID IL1110100 · Purity Score 98 (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 McHenry County cities had a PFAS sample above a 2024 EPA limit?
None of the 7 McHenry County city reports had a PFAS sample above a 2024 EPA limit in EPA's UCMR 5 testing. PFAS were detected below the limit in 3.
Is there lead in McHenry County tap water?
Utilities report lead as a 90th-percentile result from home taps. 6 of 7 McHenry 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 McHenry County water systems had drinking-water violations?
1 city in McHenry 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.
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