We read 12 results from Gswc - Claremont’s 2025 water quality report. No results over a legal limit or above a health goal.
Serves about 39,730 people · Water system ID CA1910024 · 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 |
|---|---|---|---|---|
| Chlorideaverage · range 3.9 to 100 · Source water · 2025 report, page 8 | 35 ppm | — | 250 ppm guideline | Within the guideline |
| Chlorineaverage · range 0.1 to 3.3 · Distribution system · 2025 report, page 9 | 1.7 ppm | None set | 4 ppm | Below the legal limit |
| Copper90th percentile of 30 homes tested, 0 over the action level · Customer taps · 2025 report, page 9 | 0.3 ppm | 0.3 ppm | 1.3 ppm (action level) | Below the health goal |
| Disinfection byproducts (HAA5)average · range ND to 18 · Distribution system · 2025 report, page 9 | 13 ppb | None set | 60 ppb | Below the legal limit |
| Disinfection byproducts (TTHM)average · range 6.6 to 60 · Distribution system · 2025 report, page 9 | 41 ppb | None set | 80 ppb | Below the legal limit |
| Fluorideaverage · range ND to 0.53 · Source water · 2025 report, page 8 | 0.23 ppm | 1 ppm | 2 ppm | Below the health goal |
| Lead90th percentile of 30 homes tested, 0 over the action level · Customer taps · 2025 report, page 9 | Not detected | 0.2 ppb | 15 ppb (action level) | Not detected |
| Nitrate (as N)average · range ND to 6.9 · Source water · 2025 report, page 8 | 3.4 ppm | 10 ppm | 10 ppm | Below the health goal |
| Sulfateaverage · range 23 to 56 · Source water · 2025 report, page 8 | 39 ppm | — | 250 ppm guideline | Within the guideline |
| Total dissolved solidsaverage · range 230 to 460 · Source water · 2025 report, page 8 | 320 ppm | — | 500 ppm guideline | Within the guideline |
| Hardnessaverage · range 5.67 to 19.3 · Source water · 2025 report, page 8 | 11.1 gpg (190 ppm) | — | — | Very hard |
| Sodiumaverage · range 7.8 to 68 · Source water · 2025 report, page 8 | 29 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. 2 numbers we weren’t sure about are held back until a person checks.
EPA testing for PFAS and lithium
EPA’s own nationwide testing (UCMR 5) found these in Gswc - Claremont’s water between Sep 2023 and Nov 2024. These are EPA lab results, separate from the district’s report. Anything not listed was not detected.
- PFOA12.9 pptFound in 5 of 26 samples · highest resultAbove the federal limit that takes effect in 2029 (4 ppt)
- PFOS10.4 pptFound in 1 of 26 samples · highest resultAbove the federal limit that takes effect in 2029 (4 ppt)
- PFHxS3.7 pptFound in 3 of 26 samples · highest resultNo federal limit in force for this one
- PFBS5.1 pptFound in 5 of 26 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.
PFAS ("forever chemicals")
Found: PFOA (EPA testing), PFOS (EPA testing)
What removes it: Reverse osmosis.
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