Tap water report · updated November 2026
San Francisco tap water: moderately hard water, no PFOA or PFOS found
What’s in the water San Francisco Public Utilities Commission delivers to 848,019 people, from national testing by the U.S. Environmental Protection Agency (EPA) and the utility’s own report.
Short answer
San Francisco tap water is moderately hard: about 3.6 grains per gallon (62 milligrams per liter (mg/L)), according to published water quality data from San Francisco Public Utilities Commission (2025). The U.S. Environmental Protection Agency’s (EPA’s) 2023–24 testing found no PFOA or PFOS (two PFAS “forever chemicals”) at or above its 4 parts per trillion (ppt) limit. The system had no health-based violations in the five years through September 2026.
Sources: San Francisco Public Utilities Commission 2025 data, EPA UCMR 5, EPA SDWIS 2026Q3 · Sources and method
None found
every sample under 4 ppt
Under EPA’s 4 ppt limit
EPA UCMR 5, sampled 2023–24
How San Francisco compares with the 40 systems we track
Hardness
7th softest
of 34 systems
PFOA / PFOS
Not detected
in any EPA sample
Size
23rd largest
of 40 by people served
01 · What it means
What these readings mean for your home
Each reading in plain English: what it is, how San Francisco compares with the other systems we track, and whether there’s anything to do. The tags follow EPA’s limits and reference levels where EPA has one; for hardness, which has no EPA limit, they follow the U.S. Geological Survey (USGS) scale and Minnesota’s health department. New to the acronyms? Every term, in plain English.
Hardness
Worth knowingHardness is dissolved calcium and magnesium, picked up as water runs through rock. It isn’t a health issue (EPA has no limit for it). It’s what leaves white crust on faucets, spots on glasses and scale inside your water heater. It’s measured in grains per gallon (gpg); 1 gpg is about 17 mg of minerals in a liter.
Here: At 3.6 gpg, San Francisco water is in the middle of the scale, the 7th-softest of the 34 systems we track. Some homes notice spots; many don’t.
What to do: A softener is optional. If spots bother you, a small one does the job.
What the research says: Studies tie hard water to more soap use and scale. Observational studies link it with somewhat more eczema in babies, but in the largest trial a softener didn’t improve existing eczema. The studies →
Learn more →PFAS (PFOA and PFOS)
Nothing to doPFAS are a family of thousands of manufactured chemicals used in many consumer and industrial products. They break down very slowly, which is why people call them "forever chemicals." PFOA and PFOS are the two EPA regulates most tightly. They’re measured in parts per trillion (ppt): 1 ppt is about one drop in 20 Olympic swimming pools.
Here: EPA’s 2023–24 testing found no PFOA or PFOS in San Francisco’s water at or above 4 ppt, the lowest level labs can reliably measure. 29 of the 40 systems we track can say the same; 11 had a sample over the limit.
What to do: Nothing needed by EPA’s standard. If you want PFAS lower still, the same certified filters apply.
What the research says: EPA and the National Academies link PFOA and PFOS exposure to higher cholesterol, lower vaccine response, lower birth weight and some cancers, mostly over years of drinking the water. The studies →
Learn more →Disinfectant
Nothing to doUtilities add a small amount of chlorine, or chloramine (chlorine combined with a little ammonia), so germs can’t grow in the pipes on the way to your tap. EPA allows up to 4 milligrams per liter (mg/L) of either and says water within its standards can be used for drinking, cooking and bathing.
Here: San Francisco uses chloramine, like 20 other systems we track. It lasts longer in pipes than chlorine and is harder to filter.
What to do: For taste, use catalytic carbon or a filter certified to NSF/ANSI 42 for chloramine. Fish tanks and home dialysis need it removed completely.
What the research says: Health agencies call these levels acceptable for drinking and bathing; dialysis and fish tanks are the exceptions. Studies haven’t shown shower chlorine harms skin or hair. The studies →
Learn more →Health-based violations
Nothing to doA health-based violation means the utility broke a federal drinking water rule tied to health: it went over a limit, or skipped a required treatment step. Missing a paperwork deadline doesn’t count.
Here: San Francisco’s system had none in the five years through September 2026. That’s normal for a large system: 36 of the 40 we track had none.
What to do: Nothing to do.
Learn more →How San Francisco compares: highest PFOA or PFOS sample
Parts per trillion (ppt), from EPA’s 2023–25 testing. The dashed line is EPA’s limit of 4.
San Francisco: none at or above 4 ppt. Like 28 other systems we track, EPA’s testing found no PFOA or PFOS there. These 11 did:
- Miami33.0 PFOS
- El Paso8.5 PFOS
- Fort Worth8.3 PFOA
- Philadelphia8.1 PFOA
- Louisville7.5 PFOA
- Tampa6.9 PFOS
- Dallas6.3 PFOA
- San Jose6.2 PFOS
- Cincinnati6.1 PFOS
- Columbus5.3 PFOA
- Austin4.8 PFOS
If you live in San Francisco
02 · The full results
Every PFAS result EPA recorded
EPA’s national testing (sampled 2023 to 2024) found no PFOA or PFOS at or above 4 ppt in any of 24 samples, which puts San Francisco under EPA’s limit for both.
Results from EPA’s national testing program (UCMR 5) for San Francisco Public Utilities Commission, 6 sampling points, March 2023 to March 2024. Concentrations in parts per trillion (ppt).
| Chemical | Samples | Detected | Highest | EPA limit |
|---|---|---|---|---|
| PFOA (perfluorooctanoic acid) | 24 | 0 | none | 4 |
| PFOS (perfluorooctane sulfonic acid) | 24 | 0 | none | 4 |
| PFHxS | 24 | 0 | none | 10 |
| PFNA | 24 | 0 | none | 10 |
| HFPO-DA (GenX) | 24 | 0 | none | 10 |
"None" means every sample was under EPA’s reporting level (4 ppt for PFOA). PFHxS, PFNA and HFPO-DA (GenX) are three other PFAS chemicals; EPA proposed removing their limits in May 2026, and that isn’t final.
03 · Where it comes from
The source, and who else drinks it
Hetch Hetchy Reservoir supplies up to 85 percent of the water, water from local reservoirs in Alameda and San Mateo counties is treated at the Sunol Valley and Harry Tracy plants, and in 2025 about 0.42 percent was local groundwater and 0.38 percent was treated water from Valley Water.
San Francisco Public Utilities Commission serves about 848,019 people directly, and 6 other water systems buy water from it, serving about 254,454 more. If you live in one of them, most of what’s on this page describes your water too, though hardness and disinfectant can change if your system blends in its own wells.
Hetch Hetchy water is exempt from state and federal filtration requirements.
San Francisco’s water system had no health-based violations in the five years through September 2026, according to EPA’s federal database.
Largest systems that buy from San Francisco Public Utilities Commission
- City of Redwood City90,043
- City of Milpitas81,915
- City of Burlingame32,453
- Stanford University23,817
- Menlo Park Municipal Water22,362
- Treasure Island3,864
From EPA’s federal drinking water database (SDWIS), 2026Q3: community systems with an active connection buying from CA3810011. Population served.
ZIP codes San Francisco Public Utilities Commission reports serving (13)
94103 · 94105 · 94107 · 94109 · 94110 · 94112 · 94115 · 94122 · 94124 · 94127 · 94131 · 94132 · 94134
From EPA’s UCMR 5 ZIP file. A ZIP can be served by more than one system; your water bill names yours. Look up any ZIP.
04 · Questions
San Francisco water questions
Is San Francisco tap water safe to drink?
The U.S. Environmental Protection Agency (EPA) doesn’t grade a city’s tap water as safe or unsafe; it sets limits and records violations. By that record, San Francisco’s water system had no health-based violations of federal drinking water rules in the five years through September 2026. EPA’s 2023–24 testing found no PFOA or PFOS (two PFAS “forever chemicals”) samples above its 4 parts per trillion (ppt) limit.
Is San Francisco tap water hard?
San Francisco tap water is moderately hard: about 3.6 grains per gallon (62 milligrams per liter (mg/L)), according to published water quality data from San Francisco Public Utilities Commission (2025).
Does San Francisco tap water have PFAS?
The U.S. Environmental Protection Agency’s (EPA’s) national testing (sampled 2023 to 2024) found no PFOA or PFOS (two PFAS “forever chemicals”) at or above 4 parts per trillion (ppt) in any of 24 samples, which puts San Francisco under EPA’s limit for both.
Does San Francisco use chlorine or chloramine?
Chloramine. San Francisco Public Utilities Commission (SFPUC) disinfects Hetch Hetchy water with ultraviolet light and chlorine and then adds chloramine so a disinfectant residual stays in the distribution system.
Has San Francisco’s water system had violations?
San Francisco’s water system had no health-based violations in the five years through September 2026, according to the U.S. Environmental Protection Agency’s (EPA’s) federal database.
Nearest cities we cover
Sources
- 01San Francisco Public Utilities Commission, 2025 water quality data (hardness), read 2026-11-04
- 02San Francisco Public Utilities Commission (source water)
- 03EPA, Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) occurrence data, file posted 2026-10-15
- 04EPA, Safe Drinking Water Information System via ECHO, 2026Q3 file
- 05EPA, PFAS National Primary Drinking Water Regulation, 89 FR 32532
- 06USGS Water Science School, "Hardness of Water"
EPA system ID CA3810011 · San Francisco Public Utilities Commission