Marin County Water Quality: 3 Cities Ranked by the Records
Marin County, California: 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.
Water hardnessDetected in 1 systemAesthetic, no federal health limit · USGSHighest5 gpg
- MARIN MUNICIPAL WATER DISTRICT5 gpgReporting year: 2025
31 substances tested, none detected in any systemShow
Tested in these 3 systems: MARIN MUNICIPAL WATER DISTRICT, NORTH MARIN WATER DISTRICT, PETALUMA, 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)
- Lead (90th percentile)
- Lithium
- 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)
- Perfluoroheptanoic acid (PFHpA)
- Perfluorohexanesulfonic acid (PFHxS)
- Perfluorohexanoic acid (PFHxA)
- Perfluorononanoic acid (PFNA)
- Perfluorooctanesulfonic acid (PFOS)
- Perfluorooctanoic acid (PFOA)
- 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 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 California1city reports hardness · San Rafael, 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
- San RafaelMARIN MUNICIPAL WATER DISTRICT · CA2110002188,116 served
- NovatoNORTH MARIN WATER DISTRICT · CA211000361,691 served
- PetalumaPETALUMA, CITY OF · CA491000661,427 served
Frequently asked
How does Marin County tap water compare across cities?
PurityMap ranks 3 cities in Marin 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 San Rafael's main water system: MARIN MUNICIPAL WATER DISTRICT · PWSID CA2110002 · 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 Marin County cities had a PFAS sample above a 2024 EPA limit?
None of the 3 Marin 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 0.
Is there lead in Marin County tap water?
Utilities report lead as a 90th-percentile result from home taps. 0 of 3 Marin 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 Marin County have hard water?
Hardness is published in utility water-quality reports for 1 Marin County city on record; the hardest is San Rafael at 5 grains per gallon. Hardness affects scale and appliances; it is not a health finding.
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