We read 12 results from California Water Service-S San Francisco’s 2025 water quality report. No results over a legal limit; 2 above a health goal or guideline.
Serves about 64,121 people · Water system ID CA4110009 · Read the district’s 2025 report (opens in a new tab)
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Results from the 2025 report
Each number is copied from the district’s report and links to the page it’s printed on. Where the report lists several plants, wells or purchased water, the highest is shown.
| Contaminant | Result | Health goal | Legal limit | What it means |
|---|---|---|---|---|
| Arsenicaverage · range 2.8 to 4.7 · Groundwater wells · 2025 report, page 13 | 3.4 ppb | 0.004 ppb | 10 ppb | Above the health goal850x the health goal |
| Chromium-6average · range 0.44 to 0.94 · Groundwater wells · 2025 report, page 13 | 0.63 ppb | 0.02 ppb | 10 ppb | Above the health goal32x the health goal |
| Bariumaverage · range ND to 0.13 · Groundwater wells · 2025 report, page 13 | Not detected | 2 ppm | 2 ppm | Not detected |
| Chloramineaverage · range 1 to 3.7 · Distribution system · 2025 report, page 14 | 2.8 ppm | None set | 4 ppm | Below the legal limit |
| Copper90th percentile of 31 homes tested, 0 over the action level · Customer taps · 2025 report, page 13 | 0.07 ppm | 0.3 ppm | 1.3 ppm (action level) | Below the health goal |
| Disinfection byproducts (HAA5)highest running annual average · range 7.2 to 50 · Distribution system · 2025 report, page 14 | 35 ppb | None set | 60 ppb | Below the legal limit |
| Disinfection byproducts (TTHM)highest running annual average · range 14 to 62 · Distribution system · 2025 report, page 14 | 45 ppb | None set | 80 ppb | Below the legal limit |
| Fluorideaverage · range 0.5 to 0.8 · SFPUC supplied water · 2025 report, page 13 | 0.7 ppm | 1 ppm | 2 ppm | Below the health goal |
| Lead90th percentile of 31 homes tested, 2 over the action level · Customer taps · 2025 report, page 13 | Not detected | 0.2 ppb | 15 ppb (action level) | Not detected |
| Nitrate (as N)average · range ND to 1.7 · Groundwater wells · 2025 report, page 13 | 1.2 ppm | 10 ppm | 10 ppm | Below the health goal |
| Seleniumaverage · range ND to 6.8 · Groundwater wells · 2025 report, page 13 | Not detected | 30 ppb | 50 ppb | Not detected |
| Trichloroethylene (TCE)average · range ND to 1.2 · Groundwater wells · 2025 report, page 13 | Not detected | 1.7 ppb | 5 ppb | Not detected |
Utility results describe the whole system, measured where water enters the pipes, not your tap. Your home’s plumbing can add lead or copper.
EPA testing for PFAS and lithium
EPA’s own nationwide testing (UCMR 5) found these in California Water Service-S San Francisco’s water between Jun 2024 and Mar 2025. These are EPA lab results, separate from the district’s report. Anything not listed was not detected.
- Lithium23.6 ppbFound in 2 of 6 samples · highest resultAbove EPA’s health reference level of 10 ppb (a guide, not a legal limit)
Source: EPA UCMR 5 occurrence data. The highest single result is shown; one high sample doesn’t mean every glass is that high.
What you can do
Nothing here is an emergency notice: if the district has a violation, it must tell customers directly. If you’d like to lower these at your tap, these are the treatments that remove them, and the catalog shows the models certified for each. Ranking is by certified removal; commissions never change the order.
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