Stanislaus County Water Quality: 7 Cities Ranked by the Records
Stanislaus County, California: 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.
LithiumDetected in 4 systems of 7 tested10 µg/L EPA health reference level (screening, not a legal limit) · US EPAHighest74 µg/L
- PATTERSON, CITY OF74 µg/LSample date: 2024-05-15 to 2024-12-11
- CITY OF NEWMAN-WATER DEPARTMENT40 µg/LSample date: 2023-01-23 to 2023-07-21
- MODESTO, CITY OF21 µg/LSample date: 2023-11-16 to 2024-08-14
- CERES, CITY OF15.7 µg/LSample date: 2024-10-31 to 2025-04-30
- OAKDALE, CITY OFNot detected · below 9.0 µg/L lab reporting limitSample date: 2025-02-24 to 2025-08-20
- RIVERBANK, CITY OFNot detected · below 9.0 µg/L lab reporting limitSample date: 2023-10-11 to 2024-11-18
- TURLOCK, CITY OFNot detected · below 9.0 µg/L lab reporting limitSample date: 2023-02-07 to 2023-06-01
Perfluorooctanesulfonic acid (PFOS)Detected in 2 systems of 7 tested4.0 ng/L federal MCL (2024) · US EPAHighest26 ng/L
- MODESTO, CITY OF26 ng/LSample date: 2023-11-16 to 2024-09-12
- CERES, CITY OF24 ng/LSample date: 2024-10-31 to 2025-04-30
- CITY OF NEWMAN-WATER DEPARTMENTNot detected · below 4.0 ng/L lab reporting limitSample date: 2023-01-23 to 2023-07-21
- OAKDALE, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2025-02-24 to 2025-08-20
- PATTERSON, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2024-05-15 to 2024-12-11
- RIVERBANK, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2023-10-11 to 2024-11-18
- TURLOCK, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2023-01-25 to 2023-06-01
Perfluorooctanoic acid (PFOA)Detected in 2 systems of 7 tested4.0 ng/L federal MCL (2024) · US EPAHighest12 ng/L
- CERES, CITY OF12 ng/LSample date: 2024-10-31 to 2025-04-30
- MODESTO, CITY OF8.6 ng/LSample date: 2023-11-16 to 2024-09-12
- CITY OF NEWMAN-WATER DEPARTMENTNot detected · below 4.0 ng/L lab reporting limitSample date: 2023-01-23 to 2023-07-21
- OAKDALE, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2025-02-24 to 2025-08-20
- PATTERSON, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2024-05-15 to 2024-12-11
- RIVERBANK, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2023-10-11 to 2024-11-18
- TURLOCK, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2023-01-25 to 2023-06-01
Lead (90th percentile)Detected in 3 systems of 7 tested15 µg/L federal action level · US EPAHighest21 µg/L
- RIVERBANK, CITY OF21 µg/LMonitoring period: 2024–2026 (still open)
- MODESTO, CITY OF12 µg/LMonitoring period: 2025–2027 (still open)
- TURLOCK, CITY OF0.97 µg/LMonitoring period: 2026–2026 (still open)
- CERES, CITY OFNot detectedMonitoring period: 2021–2023
- CITY OF NEWMAN-WATER DEPARTMENTNot detectedMonitoring period: 2022–2024
- OAKDALE, CITY OFNot detectedMonitoring period: 2023–2025
- PATTERSON, CITY OFNot detectedMonitoring period: 2022–2024
Water hardnessDetected in 1 systemAesthetic, no federal health limit · USGSHighest11.6 gpg
- MODESTO, CITY OF11.6 gpgReporting year: 2025
Perfluorohexanesulfonic acid (PFHxS)Detected in 2 systems of 7 tested10 ng/L federal MCL (2024) · US EPAHighest9.3 ng/L
- MODESTO, CITY OF9.3 ng/LSample date: 2023-11-16 to 2024-09-12
- CERES, CITY OF5.7 ng/LSample date: 2024-10-31 to 2025-04-30
- CITY OF NEWMAN-WATER DEPARTMENTNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-01-23 to 2023-07-21
- OAKDALE, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2025-02-24 to 2025-08-20
- PATTERSON, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-05-15 to 2024-12-11
- RIVERBANK, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-10-11 to 2024-11-18
- TURLOCK, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-01-25 to 2023-06-01
Perfluorobutanesulfonic acid (PFBS)Detected in 2 systems of 7 tested2,000 ng/L EPA health advisory (screening, not a legal limit) · US EPAHighest6.6 ng/L
- CERES, CITY OF6.6 ng/LSample date: 2024-10-31 to 2025-04-30
- MODESTO, CITY OF4.3 ng/LSample date: 2023-11-16 to 2024-09-12
- CITY OF NEWMAN-WATER DEPARTMENTNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-01-23 to 2023-07-21
- OAKDALE, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2025-02-24 to 2025-08-20
- PATTERSON, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-05-15 to 2024-12-11
- RIVERBANK, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-10-11 to 2024-11-18
- TURLOCK, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-01-25 to 2023-06-01
Perfluorohexanoic acid (PFHxA)Detected in 2 systems of 7 tested400,000 ng/L Michigan EGLE state MCL (strictest US state) · Michigan EGLEHighest7.4 ng/L
- CERES, CITY OF7.4 ng/LSample date: 2024-10-31 to 2025-04-30
- MODESTO, CITY OF6.1 ng/LSample date: 2023-11-16 to 2024-09-12
- CITY OF NEWMAN-WATER DEPARTMENTNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-01-23 to 2023-07-21
- OAKDALE, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2025-02-24 to 2025-08-20
- PATTERSON, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-05-15 to 2024-12-11
- RIVERBANK, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-10-11 to 2024-11-18
- TURLOCK, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-01-25 to 2023-06-01
2 more contaminants detectedShow
Perfluoroheptanoic acid (PFHpA)Detected in 2 systems of 7 testedNo federal or state limit; shown for transparencyHighest4.7 ng/L
- CERES, CITY OF4.7 ng/LSample date: 2024-10-31 to 2025-04-30
- MODESTO, CITY OF3.6 ng/LSample date: 2023-11-16 to 2024-09-12
- CITY OF NEWMAN-WATER DEPARTMENTNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-01-23 to 2023-07-21
- OAKDALE, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2025-02-24 to 2025-08-20
- PATTERSON, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-05-15 to 2024-12-11
- RIVERBANK, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-10-11 to 2024-11-18
- TURLOCK, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-01-25 to 2023-06-01
Perfluoropentanoic acid (PFPeA)Detected in 2 systems of 7 testedNo federal or state limit; shown for transparencyHighest8.4 ng/L
- CERES, CITY OF8.4 ng/LSample date: 2024-10-31 to 2025-04-30
- MODESTO, CITY OF6.7 ng/LSample date: 2023-11-16 to 2024-09-12
- CITY OF NEWMAN-WATER DEPARTMENTNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-01-23 to 2023-07-21
- OAKDALE, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2025-02-24 to 2025-08-20
- PATTERSON, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-05-15 to 2024-12-11
- RIVERBANK, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-10-11 to 2024-11-18
- TURLOCK, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-01-25 to 2023-06-01
22 PFAS tested, none detected in any systemShow
Tested in these 7 systems: CERES, CITY OF, CITY OF NEWMAN-WATER DEPARTMENT, MODESTO, CITY OF, OAKDALE, CITY OF, PATTERSON, CITY OF, RIVERBANK, CITY OF, TURLOCK, CITY OF
- 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)
- 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
- Open city report →
- Open city report →
- Open city report →
- Open city report →
- Open city report →
- Open city report →
- Open city report →
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.
1of 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 California1city reports hardness · Modesto, 11.6 gpg
Hard on the USGS scale. An aesthetic measure with no federal health limit.
Hard water explainedLargest water systems
- ModestoMODESTO, CITY OF · CA5010010218,915 served
- TurlockTURLOCK, CITY OF · CA501001972,888 served
- CeresCERES, CITY OF · CA501002854,513 served
- RiverbankRIVERBANK, CITY OF · CA501001825,625 served
- PattersonPATTERSON, CITY OF · CA501001724,977 served
- OakdaleOAKDALE, CITY OF · CA501001423,235 served
- NewmanCITY OF NEWMAN-WATER DEPARTMENT · CA501001312,389 served
Frequently asked
How does Stanislaus County tap water compare across cities?
PurityMap ranks 7 cities in Stanislaus 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 Patterson's main water system: PATTERSON, CITY OF · PWSID CA5010017 · Purity Score 100 (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 Stanislaus County cities had a PFAS sample above a 2024 EPA limit?
2 of 7 Stanislaus County city reports had a PFAS sample above a 2024 EPA limit in EPA's UCMR 5 testing, including Modesto (PFOS 26 ng/L), Ceres (PFOS 24 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 Stanislaus County tap water?
Utilities report lead as a 90th-percentile result from home taps. 3 of 7 Stanislaus County cities reported a value above zero, and 1 city 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 Stanislaus County water systems had drinking-water violations?
3 cities in Stanislaus County have 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 Stanislaus County have hard water?
Hardness is published in utility water-quality reports for 1 Stanislaus County city on record; the hardest is Modesto at 11.6 grains per gallon. Hardness affects scale and appliances; it is not a health finding.
Follow Stanislaus County's water
Get an email when a city record in the county changes. Or go straight to the filters certified for what was found here.
Record changes only
We email when places in Stanislaus County get new results. Unsubscribe any time.
Follow Stanislaus County's water →