Drinking water quality · 2024
· Verified
· PWSID CA4110008
What's in San Mateo, CA tap water
Every one of the 10 core regulated contaminants reported for San Mateo, CA came in below its federal limit.
- !10 of 27 core regulated contaminants reported — 17 never appear in this report
- ✓Nothing over a federal limit
- ✓No open federal violations
+How this score is calculated
Every system starts at 100. Points come off for measured levels, for the federal violation record, and for how much of the core regulated set the utility actually reported. All three inputs are the utility's own published numbers and EPA's own records.
- −0 contaminants at or above a federal limit
- −0 contaminants within 20% of a limit
- −0 open health-based violations
- −0 open monitoring / reporting violations
- −0 health-based violations resolved in the last 5 years
- −14 core regulated contaminants never reported (10/27)
A 90–100 · B 80–89 · C 70–79 · D 60–69 · F below 60. A system reporting under a third of the core set is capped at C however clean its numbers look — a short report is not a clean bill of health.
Full grading methodology, constant for constant →+30 contaminants were measured and came in below the limitShow all
| Contaminant | Measured | Federal limit |
|---|---|---|
| Chloramine | 2.8 mg/L | 4 mg/L |
| HAA5 | 40 ug/L | 60 ug/L |
| TTHM | 41 ug/L | 80 ug/L |
| Turbidity | 0.4 NTU | 1 NTU |
| Fluoride | 0.7 mg/L | 4 mg/L |
| Chlorate | 144 ug/L | 800 ug/L |
| Bromide | Not detected ug/L | — |
| Chloride | 9.3 mg/L | — |
| Nitrate | Not detected mg/L | 10 mg/L |
| Sulfate | 18 mg/L | — |
| Aluminum | Not detected mg/L | — |
| Boron | 0.04 mg/L | 1 mg/L |
| Calcium | 15 mg/L | — |
| Chromium, Hexavalent | 0.1 ug/L | — |
| Copper | Not detected mg/L | 1.3 mg/L |
| Iron | 14 ug/L | — |
| Lead | Not detected ug/L | 15 ug/L |
| Lithium | Not detected mg/L | — |
| Magnesium | 5.7 mg/L | — |
| Manganese | Not detected ug/L | — |
| Silica | 7.5 mg/L | — |
| Sodium | 16 mg/L | — |
| Escherichia coli (E. coli) | 0 | — |
| Giardia lamblia | 0.02 | 0 |
| Alkalinity | 60 mg/L | — |
| Hardness | 60 mg/L | — |
| pH | 8.9 | — |
| Specific Conductance | 193 | — |
| TOC | 1.5 mg/L | — |
| Total Dissolved Solids | 102 mg/L | — |
What this report doesn't tell you
17 of the 27 contaminants a community water system normally reports do not appear anywhere in San Mateo, CA's data. Absent is not the same as absent-from-the-water — it means nobody published a number.
+Full detail: PFAS testing, water source, historical monitoring, and the federal violation record
Where your water comes from · EPA SDWIS
San Mateo, CA buys its drinking water from SAN FRANCISCO REGIONAL WATER SYSTEM.
Source
Treatment
Distribution
Also buys water from SAN FRANCISCO REGIONAL WATER SYSTEM.
Compliance history
Federal Safe Drinking Water Act violation & enforcement records (EPA SDWIS). A violation is a regulatory determination by the state or EPA — separate from the measured levels above.
- Treatment technique violationHealth-based1 violation on record · most recent Jun 1993resolved
- Maximum contaminant level exceededHealth-based1 violation on record · most recent Oct 1992resolved
Source: EPA SDWIS / ECHO. View the full federal record on EPA ECHO ↗