Sonoma County Water Quality: 5 Cities Ranked by the Records
Sonoma County, California: 5 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 3 systems of 5 tested10 µg/L EPA health reference level (screening, not a legal limit) · US EPAHighest96 µg/L
- SANTA ROSA, CITY OF96 µg/LSample date: 2024-05-09 to 2024-11-05
- SONOMA, CITY OF40 µg/LSample date: 2023-07-19 to 2024-01-16
- ROHNERT PARK, CITY OF39 µg/LSample date: 2024-04-09 to 2024-10-22
- HEALDSBURG, CITY OFNot detected · below 9.0 µg/L lab reporting limitSample date: 2024-05-21 to 2025-05-20
- WINDSOR, TOWN OFNot detected · below 9.0 µg/L lab reporting limitSample date: 2025-01-08 to 2025-07-16
Perfluorooctanoic acid (PFOA)Detected in 1 system of 5 tested4.0 ng/L federal MCL (2024) · US EPAHighest6.2 ng/L
- SONOMA, CITY OF6.2 ng/LSample date: 2023-07-19 to 2024-01-16
- HEALDSBURG, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2024-05-21 to 2025-05-20
- ROHNERT PARK, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2024-04-09 to 2024-10-22
- SANTA ROSA, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2024-05-09 to 2024-12-04
- WINDSOR, TOWN OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2025-01-08 to 2025-07-16
Perfluorooctanesulfonic acid (PFOS)Detected in 1 system of 5 tested4.0 ng/L federal MCL (2024) · US EPAHighest4.5 ng/L
- ROHNERT PARK, CITY OF4.5 ng/LSample date: 2024-04-09 to 2024-10-22
- HEALDSBURG, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2024-05-21 to 2025-05-20
- SANTA ROSA, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2024-05-09 to 2024-12-04
- SONOMA, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2023-07-19 to 2024-01-16
- WINDSOR, TOWN OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2025-01-08 to 2025-07-16
Perfluorohexanesulfonic acid (PFHxS)Detected in 2 systems of 5 tested10 ng/L federal MCL (2024) · US EPAHighest5.7 ng/L
- ROHNERT PARK, CITY OF5.7 ng/LSample date: 2024-04-09 to 2024-10-22
- HEALDSBURG, CITY OF4.5 ng/LSample date: 2024-05-21 to 2025-05-20
- SANTA ROSA, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-05-09 to 2024-12-04
- SONOMA, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-07-19 to 2024-01-16
- WINDSOR, TOWN OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2025-01-08 to 2025-07-16
Lead (90th percentile)Detected in 1 system of 5 tested15 µg/L federal action level · US EPAHighest1.32 µg/L
- SANTA ROSA, CITY OF1.32 µg/LMonitoring period: 2023–2025
- HEALDSBURG, CITY OFNot detectedMonitoring period: 2021–2023
- ROHNERT PARK, CITY OFNot detectedMonitoring period: 2023–2025
- SONOMA, CITY OFNot detectedMonitoring period: 2021–2023
- WINDSOR, TOWN OFNot detectedMonitoring period: 2023–2025
Perfluorobutanesulfonic acid (PFBS)Detected in 1 system of 5 tested2,000 ng/L EPA health advisory (screening, not a legal limit) · US EPAHighest5.2 ng/L
- HEALDSBURG, CITY OF5.2 ng/LSample date: 2024-05-21 to 2025-05-20
- ROHNERT PARK, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-04-09 to 2024-10-22
- SANTA ROSA, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-05-09 to 2024-12-04
- SONOMA, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-07-19 to 2024-01-16
- WINDSOR, TOWN OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2025-01-08 to 2025-07-16
Perfluorohexanoic acid (PFHxA)Detected in 1 system of 5 tested400,000 ng/L Michigan EGLE state MCL (strictest US state) · Michigan EGLEHighest6.1 ng/L
- SONOMA, CITY OF6.1 ng/LSample date: 2023-07-19 to 2024-01-16
- HEALDSBURG, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-05-21 to 2025-05-20
- ROHNERT PARK, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-04-09 to 2024-10-22
- SANTA ROSA, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-05-09 to 2024-12-04
- WINDSOR, TOWN OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2025-01-08 to 2025-07-16
Water hardnessDetected in 1 systemAesthetic, no federal health limit · USGSHighest6.5 gpg
- SANTA ROSA, CITY OF6.5 gpgReporting year: 2025
2 more contaminants detectedShow
1H, 1H, 2H, 2H-perfluorooctane sulfonic acid (6:2 FTS)Detected in 1 system of 5 testedNo federal or state limit; shown for transparencyHighest7.1 ng/L
- ROHNERT PARK, CITY OF7.1 ng/LSample date: 2024-04-09 to 2024-10-22
- HEALDSBURG, CITY OFNot detected · below 5.0 ng/L lab reporting limitSample date: 2024-05-21 to 2025-05-20
- SANTA ROSA, CITY OFNot detected · below 5.0 ng/L lab reporting limitSample date: 2024-05-09 to 2024-12-04
- SONOMA, CITY OFNot detected · below 5.0 ng/L lab reporting limitSample date: 2023-07-19 to 2024-01-16
- WINDSOR, TOWN OFNot detected · below 5.0 ng/L lab reporting limitSample date: 2025-01-08 to 2025-07-16
Perfluorododecanoic acid (PFDoA)Detected in 1 system of 5 testedNo federal or state limit; shown for transparencyHighest3.1 ng/L
- HEALDSBURG, CITY OF3.1 ng/LSample date: 2024-05-21 to 2025-05-20
- ROHNERT PARK, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-04-09 to 2024-10-22
- SANTA ROSA, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-05-09 to 2024-12-04
- SONOMA, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-07-19 to 2024-01-16
- WINDSOR, TOWN OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2025-01-08 to 2025-07-16
22 PFAS tested, none detected in any systemShow
Tested in these 5 systems: HEALDSBURG, CITY OF, ROHNERT PARK, CITY OF, SANTA ROSA, CITY OF, SONOMA, CITY OF, WINDSOR, TOWN 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)
- 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)
- Perfluoroheptanesulfonic acid (PFHpS)
- Perfluoroheptanoic acid (PFHpA)
- Perfluorononanoic acid (PFNA)
- Perfluoropentanesulfonic acid (PFPeS)
- Perfluoropentanoic acid (PFPeA)
- 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 5 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 · Santa Rosa, 6.5 gpg
None above 7 gpg, the USGS threshold for hard water. An aesthetic measure with no federal health limit.
Hard water explainedLargest water systems
- Santa RosaSANTA ROSA, CITY OF · CA4910009178,452 served
- Rohnert ParkROHNERT PARK, CITY OF · CA491001443,821 served
- WindsorWINDSOR, TOWN OF · CA491001725,561 served
- HealdsburgHEALDSBURG, CITY OF · CA491000510,972 served
- SonomaSONOMA, CITY OF · CA491001210,619 served
Frequently asked
How does Sonoma County tap water compare across cities?
PurityMap ranks 5 cities in Sonoma 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: WINDSOR, TOWN OF · PWSID CA4910017 · 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 Sonoma County cities had a PFAS sample above a 2024 EPA limit?
2 of 5 Sonoma County city reports had a PFAS sample above a 2024 EPA limit in EPA's UCMR 5 testing, including Sonoma (PFOA 6.2 ng/L), Rohnert Park (PFOS 4.5 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 3.
Is there lead in Sonoma County tap water?
Utilities report lead as a 90th-percentile result from home taps. 1 of 5 Sonoma 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.
Does Sonoma County have hard water?
Hardness is published in utility water-quality reports for 1 Sonoma County city on record; the hardest is Santa Rosa at 6.5 grains per gallon. Hardness affects scale and appliances; it is not a health finding.
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