We read 25 results from Gswc-South San Gabriel’s 2025 water quality report. No results over a legal limit; 4 above a health goal or guideline.
Serves about 26,240 people · Water system ID CA1910223 · 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 |
|---|---|---|---|---|
| Bromateaverage · range ND to 12 · Distribution system · 2025 report, page 9 | 3 ppb | 0.1 ppb | 10 ppb | Above the health goal30x the health goal |
| Chromium-6average · range ND to 7.2 · Source water · 2025 report, page 8 | 3.8 ppb | 0.02 ppb | 10 ppb | Above the health goal190x the health goal |
| Copper90th percentile of 30 homes tested, 0 over the action level · sampled 2023 · Customer taps · 2025 report, page 9 | 0.6 ppm | 0.3 ppm | 1.3 ppm (action level) | Above the health goal2x the health goal |
| Uraniumaverage · range ND to 4.92 · printed as 2.2 pCi/L · Source water · 2025 report, page 8 | 3.28 ppb | 0.6 ppb | 30 ppb | Above the health goal5.5x the health goal |
| Chlorideaverage · range 18 to 98 · Source water · 2025 report, page 8 | 50 ppm | — | 250 ppm guideline | Within the guideline |
| Chlorineaverage · range 0.2 to 3.9 · Distribution system · 2025 report, page 9 | 1.6 ppm | None set | 4 ppm | Below the legal limit |
| Disinfection byproducts (HAA5)average · range ND to 4.8 · Distribution system · 2025 report, page 9 | 2.1 ppb | None set | 60 ppb | Below the legal limit |
| Disinfection byproducts (TTHM)average · range ND to 37 · Distribution system · 2025 report, page 9 | 12 ppb | None set | 80 ppb | Below the legal limit |
| Fluorideaverage · range 0.4 to 0.8 · Source water · 2025 report, page 8 | 0.6 ppm | 1 ppm | 2 ppm | Below the health goal |
| Lead90th percentile of 30 homes tested, 0 over the action level · sampled 2023 · Customer taps · 2025 report, page 9 | Not detected | 0.2 ppb | 15 ppb (action level) | Not detected |
| Nitrate (as N)average · range ND to 3.8 · Source water · 2025 report, page 8 | 1.6 ppm | 10 ppm | 10 ppm | Below the health goal |
| Perchlorateaverage · range ND to 1.4 · Source water · 2025 report, page 8 | Not detected | 1 ppb | 6 ppb | Not detected |
| pHaverage · range 7.9 to 8.3 · Source water · 2025 report, page 8 | 8 | — | — | Normal range |
| Sulfateaverage · range 50 to 212 · Source water · 2025 report, page 8 | 100 ppm | — | 250 ppm guideline | Within the guideline |
| Tetrachloroethylene (PCE)average · range ND to 1 · Source water · 2025 report, page 8 | 0.06 ppb | 0.06 ppb | 5 ppb | Below the health goal |
| Total dissolved solidsaverage · range 310 to 617 · Source water · 2025 report, page 8 | 440 ppm | — | 500 ppm guideline | Within the guideline |
| Turbidity (cloudiness)highest measured · Treated surface water · 2025 report, page 8 | 0.06 NTU | None set | 1 NTU | Below the legal limit |
| Alkalinityaverage · range 95 to 200 · Source water · 2025 report, page 8 | 160 ppm | None set | None | No health limit |
| Calciumaverage · range 43 to 82 · Source water · 2025 report, page 8 | 62 ppm | None set | None | No health limit |
| Conductivityaverage · range 480 to 981 · Source water · 2025 report, page 8 | 690 µS/cm | None set | None | No health limit |
| Hardnessaverage · range 11.1 to 18.1 · Source water · 2025 report, page 8 | 14 gpg (240 ppm) | — | — | Very hard |
| Lithiumaverage · sampled 2024 · Source water · 2025 report, page 8 | 14 ppb | None set | None | No health limit |
| Magnesiumaverage · range 16 to 26 · Source water · 2025 report, page 8 | 21 ppm | None set | None | No health limit |
| Potassiumaverage · range 1.3 to 5 · Source water · 2025 report, page 8 | 2.3 ppm | None set | None | No health limit |
| Sodiumaverage · range 26 to 100 · Source water · 2025 report, page 8 | 50 ppm | None set | None | No health limit |
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 Gswc-South San Gabriel’s water between Oct 2023 and Jul 2024. These are EPA lab results, separate from the district’s report. Anything not listed was not detected.
- Lithium57 ppbFound in 4 of 8 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.
Copper
Found: Copper
What removes it: Reverse osmosis.
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