We read 27 results from Gswc - Southwest’s 2025 water quality report. No results over a legal limit; 1 above a health goal or guideline.
Serves about 277,740 people · Water system ID CA1910155 · 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 | 4.1 ppb | 0.1 ppb | 10 ppb | Above the health goal41x the health goal |
| Aluminumaverage · range ND to 0.1 · Source water · 2025 report, page 8 | Not detected | — | 0.2 ppm guideline | Not detected |
| Arsenicaverage · range ND to 3.1 · Source water · 2025 report, page 8 | Not detected | 0.004 ppb | 10 ppb | Not detected |
| Bariumaverage · range ND to 0.13 · Source water · 2025 report, page 8 | Not detected | 2 ppm | 2 ppm | Not detected |
| Chloramineaverage · range 0.1 to 4.5 · Distribution system · 2025 report, page 9 | 2.4 ppm | None set | 4 ppm | Below the legal limit |
| Chlorideaverage · range 24 to 99 · Source water · 2025 report, page 8 | 51 ppm | — | 250 ppm guideline | Within the guideline |
| Copper90th percentile of 107 homes tested, 0 over the action level · sampled 2023 · Customer taps (107 samples) · 2025 report, page 9 | 0.12 ppm | 0.3 ppm | 1.3 ppm (action level) | Below the health goal |
| Disinfection byproducts (HAA5)average · range ND to 10 · Distribution system · 2025 report, page 9 | 10 ppb | None set | 60 ppb | Below the legal limit |
| Disinfection byproducts (TTHM)average · range 4 to 47 · Distribution system · 2025 report, page 9 | 35 ppb | None set | 80 ppb | Below the legal limit |
| Fluorideaverage · range 0.4 to 0.7 · Source water · 2025 report, page 8 | 0.6 ppm | 1 ppm | 2 ppm | Below the health goal |
| Gross alpha (radioactivity)average · range ND to 7.1 · sampled 2023 · Source water · 2025 report, page 8 | Not detected | 0 pCi/L | 15 pCi/L | Not detected |
| Gross beta (radioactivity)average · range ND to 6 · Source water · 2025 report, page 8 | Not detected | 0 pCi/L | 50 pCi/L | Not detected |
| Ironaverage · range ND to 0.52 · printed as ND µg/L · Source water · 2025 report, page 8 | Not detected | — | 0.3 ppm guideline | Not detected |
| Lead90th percentile of 107 homes tested, 1 over the action level · sampled 2023 · Customer taps (107 samples) · 2025 report, page 9 | Not detected | 0.2 ppb | 15 ppb (action level) | Not detected |
| Manganeseaverage · range ND to 0.05 · printed as ND µg/L · Source water · 2025 report, page 8 | Not detected | — | 0.05 ppm guideline | Not detected |
| pHaverage · range 8.1 to 8.4 · Source water · 2025 report, page 8 | 8.2 | — | — | Normal range |
| Sulfateaverage · range 18 to 218 · Source water · 2025 report, page 8 | 89 ppm | — | 250 ppm guideline | Within the guideline |
| Total dissolved solidsaverage · range 293 to 625 · Source water · 2025 report, page 8 | 386 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 |
| Uraniumaverage · range ND to 4.47 · printed as ND pCi/L · Source water · 2025 report, page 8 | Not detected | 0.6 ppb | 30 ppb | Not detected |
| Alkalinityaverage · range 93 to 180 · Source water · 2025 report, page 8 | 150 ppm | None set | None | No health limit |
| Calciumaverage · range 31 to 70 · Source water · 2025 report, page 8 | 50 ppm | None set | None | No health limit |
| Hardnessaverage · range 8.01 to 16.4 · Source water · 2025 report, page 8 | 11.1 gpg (190 ppm) | — | — | Very hard |
| Lithiumaverage · range ND to 51 · Source water · 2025 report, page 8 | Not detected | None set | None | No health limit |
| Magnesiumaverage · range 11 to 25 · Source water · 2025 report, page 8 | 15 ppm | None set | None | No health limit |
| Potassiumaverage · range 2.8 to 5.1 · Source water · 2025 report, page 8 | 3.9 ppm | None set | None | No health limit |
| Sodiumaverage · range 41 to 100 · Source water · 2025 report, page 8 | 57 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 - Southwest’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.
- Lithium51.3 ppbFound in 4 of 18 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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