We read 13 results from Cwsc Los Altos Suburban’s 2025 water quality report. No results over a legal limit; 2 above a health goal or guideline.
Serves about 70,175 people · Water system ID CA4310001 · 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 |
|---|---|---|---|---|
| Chromium-6average · range 0.23 to 2.6 · Groundwater wells · 2025 report, page 13 | 1.4 ppb | 0.02 ppb | 10 ppb | Above the health goal70x the health goal |
| Copper90th percentile of 31 homes tested, 0 over the action level · Customer taps · 2025 report, page 13 | 0.38 ppm | 0.3 ppm | 1.3 ppm (action level) | Above the health goal1.3x the health goal |
| Bariumaverage · range ND to 0.2 · Groundwater wells · 2025 report, page 13 | Not detected | 2 ppm | 2 ppm | Not detected |
| Chloramineaverage · range ND to 3 · Distribution system · 2025 report, page 14 | 1.5 ppm | None set | 4 ppm | Below the legal limit |
| Disinfection byproducts (HAA5)highest running annual average · Distribution system · 2025 report, page 13 | 17 ppb | None set | 60 ppb | Below the legal limit |
| Disinfection byproducts (TTHM)highest running annual average · Distribution system · 2025 report, page 13 | 40 ppb | None set | 80 ppb | Below the legal limit |
| Fluorideaverage · range ND to 0.22 · Groundwater wells · 2025 report, page 13 | Not detected | 1 ppm | 2 ppm | Not detected |
| Lead90th percentile of 31 homes tested, 0 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 1.3 to 7.8 · Groundwater wells · 2025 report, page 13 | 4.1 ppm | 10 ppm | 10 ppm | Below the health goal |
| Perchlorateaverage · range ND to 2.6 · Groundwater wells · 2025 report, page 13 | Not detected | 1 ppb | 6 ppb | Not detected |
| Turbidity (cloudiness)highest measured · Valley Water treated water · 2025 report, page 14 | 0.47 NTU | None set | 1 NTU | Below the legal limit |
| Boronaverage · range ND to 0.23 · Groundwater wells · 2025 report, page 15 | 0.12 ppm | None set | None | No health limit |
| Vanadiumaverage · range 3.7 to 9.3 · Groundwater wells · 2025 report, page 15 | 6.4 ppb | 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 Cwsc Los Altos Suburban’s water between Jun 2023 and Mar 2025. These are EPA lab results, separate from the district’s report. Anything not listed was not detected.
- PFHxS3.5 pptFound in 2 of 36 samples · highest resultNo federal limit in force for this one
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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