We read 9 results from California Water Service Co - Westlake’s 2025 water quality report. No results over a legal limit or above a health goal.
Serves about 19,533 people · Water system ID CA5610016 · 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 |
|---|---|---|---|---|
| Chloramineaverage · range 0.36 to 2.7 · Distribution system · 2025 report, page 13 | 1.8 ppm | None set | 4 ppm | Below the legal limit |
| Chlorideaverage · range 96 to 100 · Calleguas MWD (94% of supply) · 2025 report, page 16 | 99 ppm | — | 250 ppm guideline | Within the guideline |
| Copper90th percentile of 30 homes tested, 0 over the action level · sampled 2024 · Customer taps · 2025 report, page 13 | 0.22 ppm | 0.3 ppm | 1.3 ppm (action level) | Below the health goal |
| Disinfection byproducts (HAA5)highest running annual average · range 7 to 14 · Distribution system · 2025 report, page 13 | 9.8 ppb | None set | 60 ppb | Below the legal limit |
| Disinfection byproducts (TTHM)highest running annual average · range ND to 28 · Distribution system · 2025 report, page 13 | 22 ppb | None set | 80 ppb | Below the legal limit |
| Sulfateaverage · range 102 to 104 · Calleguas MWD (94% of supply) · 2025 report, page 16 | 103 ppm | — | 250 ppm guideline | Within the guideline |
| Total dissolved solidsaverage · range 400 to 470 · Calleguas MWD (94% of supply) · 2025 report, page 16 | 437 ppm | — | 500 ppm guideline | Within the guideline |
| Boronaverage · Calleguas MWD (94% of supply) · 2025 report, page 16 | 0.3 ppm | None set | None | No health limit |
| Conductivityaverage · range 729 to 765 · Calleguas MWD (94% of supply) · 2025 report, page 16 | 752 µS/cm | 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. 1 number we weren’t sure about is held back until a person checks.
EPA testing for PFAS and lithium
EPA’s own nationwide testing (UCMR 5) found these in California Water Service Co - Westlake’s water between Jun 2023 and Mar 2024. These are EPA lab results, separate from the district’s report. Anything not listed was not detected.
- Lithium13.8 ppbFound in 4 of 4 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 in this report is above a health goal or legal limit. If you’re bothered by taste, smell, hardness or spots, or your home has older pipes, the filter catalog and buyer questions can help you pick, and a test of your own tap shows what your plumbing adds.
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