Water Health Check Report
San Francisco, CA
San Francisco Public Utilities Commission · Surface water source · Hetch Hetchy Reservoir (Sierra Nevada snowmelt via Hetch Hetchy Aqueduct; supplemented by regional surface reservoirs)
Poor — with 6 concerns
San Francisco Public Utilities Commission has 2 contaminants above EPA legal limits and 4 above EWG health guidelines. No PFAS detected in UCMR5 sampling
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PFAS—25 compounds tested, none detected
EPA UCMR5 monitoring found no PFAS above the minimum reporting level in San Francisco's water supply. This is a meaningful result: PFAS have been detected in roughly half of all tested US public water systems.
Source: EPA UCMR5 (2023–2025) · 25 compounds tested including all regulated PFAS
Source water vs. distribution system
Hetch Hetchy is one of the most pristine municipal water sources in the United States —federally protected Sierra Nevada snowmelt collected in Yosemite National Park. The source water at the reservoir genuinely is excellent. What this report reflects is different: SFPUC monitors water quality at distribution points across the city, measuring what reaches the tap after travelling hundreds of miles through the Peninsula aqueduct system.
Two contaminants are detected above regulatory limits in that distribution monitoring. Chromium-6 at 16.3 ppb exceeds California's 10 ppb MCL—the Peninsula corridor runs through areas with industrial history where Cr-6 can enter from infrastructure or geological deposits. Perchlorate at 0.43 ppb exceeds the 2026 federal MCL of 0.056 ppb, a pattern seen across California water systems due to the aerospace manufacturing legacy in the region.
These findings are from SFPUC distribution monitoring (CA3810011), not reservoir sampling. A filter certified for Cr-6 and perchlorate removal addresses the tap-level exposure.
Contaminants tested
39 total · 4 above EWG guideline| Contaminant | Level | Status |
|---|---|---|
Chromium-6 (hexavalent chromium) CAS 18540-29-9 | 16.2 ppb | Above EPA limit |
Perchlorate CAS 14797-73-0 | 0.43 ppb | Above EPA limit |
Haloacetic acids (HAA5) CAS Various | 34.1 ppb | Above guideline |
Total trihalomethanes (TTHMs) CAS Various | 45.9 ppb | Above guideline |
Arsenic CAS 7440-38-2 | 0.23 ppb | Above guideline |
Nitrate CAS 14797-55-8 | 7.5 ppm | Above guideline |
Manganese CAS 7439-96-5 | 25.4 ppb | Within limits |
Copper CAS 7440-50-8 | 0.07 ppm | Within limits |
Mercury (inorganic) CAS 7439-97-6 | ND | Not detected |
Selenium CAS 7782-49-2 | ND | Not detected |
Lithium CAS 7439-93-2 | ND | Not detected |
Barium CAS 7440-39-3 | ND | Not detected |
ND | Not detected | |
8:2 FTS (8:2 fluorotelomer sulfonic acid) CAS 39108-34-4 | ND | Not detected |
Fluoride CAS 16984-48-8 | ND | Not detected |
Lead CAS 7439-92-1 | ND | Not detected |
4:2 FTS (4:2 fluorotelomer sulfonic acid) CAS 757124-72-4 | ND | Not detected |
PFPeA (perfluoropentanoic acid) CAS 2706-90-3 | ND | Not detected |
PFPeS (perfluoropentane sulfonic acid) CAS 2706-91-4 | ND | Not detected |
PFHpS (perfluoroheptane sulfonic acid) CAS 375-92-8 | ND | Not detected |
PFBS (perfluorobutane sulfonic acid) CAS 375-73-5 | ND | Not detected |
ND | Not detected | |
PFUnA (perfluoroundecanoic acid) CAS 2058-94-8 | ND | Not detected |
ADONA (4,8-dioxa-3H-perfluorononanoic acid) CAS 919005-14-4 | ND | Not detected |
ND | Not detected | |
ND | Not detected | |
HFPO-DA / GenX (hexafluoropropylene oxide dimer acid) CAS 13252-13-6 | ND | Not detected |
PFHxA (perfluorohexanoic acid) CAS 307-24-4 | ND | Not detected |
PFDoA (perfluorododecanoic acid) CAS 307-55-1 | ND | Not detected |
PFDA (perfluorodecanoic acid) CAS 335-76-2 | ND | Not detected |
PFOA (perfluorooctanoic acid) CAS 335-67-1 | ND | Not detected |
PFHpA (perfluoroheptanoic acid) CAS 375-85-9 | ND | Not detected |
PFNA (perfluorononanoic acid) CAS 375-95-1 | ND | Not detected |
PFHxS (perfluorohexane sulfonic acid) CAS 355-46-4 | ND | Not detected |
PFOS (perfluorooctane sulfonate) CAS 1763-23-1 | ND | Not detected |
PFBA (perfluorobutanoic acid) CAS 375-22-4 | ND | Not detected |
6:2 FTS (6:2 fluorotelomer sulfonic acid) CAS 27619-97-2 | ND | Not detected |
PFTrDA (perfluorotridecanoic acid) CAS 72629-94-8 | ND | Not detected |
PFTA (perfluorotetradecanoic acid) CAS 376-06-7 | ND | Not detected |
Filter recommendation
6 contaminants above guidelines. Here's what removes them.
A guided 4-question flow matches you to the right filter for your setup, budget, and household.
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Data sources
Status flags compare detected levels against both EPA legal limits and EWG health-based guidelines—which are stricter and science-derived, independent of political feasibility.