We read 22 results from California Water Service - Stockton’s 2025 water quality report. No results over a legal limit; 5 above a health goal or guideline.
Serves about 176,266 people · Water system ID CA3910001 · Read the district’s 2025 report (opens in a new tab)
Open this district in the water lookupCompare with your own test results, see the district map and get matched filters.
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 ND to 8.8 · Groundwater wells · 2025 report, page 13 | 3.7 ppb | 0.004 ppb | 10 ppb | Above the health goal925x the health goal |
| Chromium-6average · range ND to 7 · Groundwater wells · 2025 report, page 13 | 2.1 ppb | 0.02 ppb | 10 ppb | Above the health goal105x the health goal |
| Gross alpha (radioactivity)highest measured · range ND to 7.9 · Groundwater wells · 2025 report, page 13 | 7.9 pCi/L | 0 pCi/L | 15 pCi/L | Above the health goalThe health goal is zero |
| PFOS (a PFAS)highest measured · range ND to 8.4 · Groundwater wells · 2025 report, page 15 | 8.4 ppt | 1 ppt | 4 ppt from 2029 | Above the federal limit that takes effect in 20292.1x the 4 ppt federal limit that takes effect in 2029Not a violation yet: EPA's 4 ppt limit is final, but water systems don't have to meet it until 2029. |
| Uraniumaverage · range ND to 8.64 · printed as 2.1 pCi/L · Groundwater wells · 2025 report, page 13 | 3.13 ppb | 0.6 ppb | 30 ppb | Above the health goal5.2x the health goal |
| Aluminumhighest measured · range ND to 0.08 · Groundwater wells · 2025 report, page 13 | 0.08 ppm | — | 0.2 ppm guideline | Within the guideline |
| Bariumaverage · range ND to 0.3 · Groundwater wells · 2025 report, page 13 | 0.13 ppm | 2 ppm | 2 ppm | Below the health goal |
| Chlorineaverage · range ND to 2.9 · Distribution system · 2025 report, page 14 | 0.75 ppm | None set | 4 ppm | Below the legal limit |
| Copper90th percentile of 51 homes tested, 0 over the action level · sampled 2024 · Customer taps (51 sites) · 2025 report, page 13 | Not detected | 0.3 ppm | 1.3 ppm (action level) | Not detected |
| Disinfection byproducts (HAA5)highest running annual average · range ND to 60 · Distribution system · 2025 report, page 14 | 26 ppb | None set | 60 ppb | Below the legal limit |
| Disinfection byproducts (TTHM)highest running annual average · range 2.6 to 78 · Distribution system · 2025 report, page 14 | 60 ppb | None set | 80 ppb | Below the legal limit |
| Fluoridehighest measured · range ND to 0.12 · Groundwater wells · 2025 report, page 13 | 0.12 ppm | 1 ppm | 2 ppm | Below the health goal |
| Ironhighest measured · range ND to 0.19 · printed as 190 ppb · Groundwater wells · 2025 report, page 15 | 0.19 ppm | — | 0.3 ppm guideline | Within the guideline |
| Lead90th percentile of 51 homes tested, 0 over the action level · sampled 2024 · Customer taps (51 sites) · 2025 report, page 13 | Not detected | 0.2 ppb | 15 ppb (action level) | Not detected |
| Manganesehighest measured · range ND to 0.04 · printed as 36 ppb · Groundwater wells · 2025 report, page 15 | 0.04 ppm | — | 0.05 ppm guideline | Within the guideline |
| Nitrate (as N)average · range ND to 6.9 · Groundwater wells · 2025 report, page 13 | 1.7 ppm | 10 ppm | 10 ppm | Below the health goal |
| PFHxS (a PFAS)highest measured · range ND to 3.6 · Groundwater wells · 2025 report, page 15 | 3.6 ppt | None set | 10 ppt from 2029 | Below the legal limit |
| Total dissolved solidsaverage · range 200 to 460 · Groundwater wells, highest of 2 sources · 2025 report, page 15 | 289 ppm | — | 500 ppm guideline | Within the guideline |
| Turbidity (cloudiness)highest measured · SEWD surface water · 2025 report, page 14 | 0.12 NTU | None set | 1 NTU | Below the legal limit |
| Hardnessaverage · range 1.29 to 17 · Groundwater wells, highest of 2 sources · 2025 report, page 16 | 8.77 gpg (150 ppm) | — | — | Hard |
| Sodiumaverage · range 7.6 to 44 · Groundwater wells, highest of 2 sources · 2025 report, page 16 | 23 ppm | None set | None | No health limit |
| Vanadiumaverage · range ND to 32 · Groundwater wells · 2025 report, page 15 | 17 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 California Water Service - Stockton’s water between Jan 2025 and Mar 2026. These are EPA lab results, separate from the district’s report. Anything not listed was not detected.
- PFOS5.2 pptFound in 2 of 28 samples · highest resultAbove the federal limit that takes effect in 2029 (4 ppt)
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.
Radium and uranium
Found: Gross alpha (radioactivity), Uranium
What removes it: Reverse osmosis.
PFAS ("forever chemicals")
Found: PFOS (a PFAS), PFOS (EPA testing)
What removes it: Reverse osmosis.
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