Drinking water quality · 2024
· Verified
What's in California Water Service - San Mateo, CA tap water
39 contaminants were measured in the California Water Service - San Mateo, CA water system's 2024 annual report. Each is shown below against its federal limit.
- Reporting year
- 2024
- Contaminants measured
- 39
- Over federal limit
- 0
- Approaching the limit
- 0
- Service area
- CA
state-level CCR
Where your water comes from · EPA SDWIS
California Water Service - San Mateo, CA buys its drinking water from SAN FRANCISCO REGIONAL WATER SYSTEM.
Source
0sources
Treatment
0treatment plants
Distribution
0storage units
Also buys water from SAN FRANCISCO REGIONAL WATER SYSTEM.
Source: EPA SDWIS facilities inventory. Methodology.
Disinfectants
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| ChloramineA longer-lasting disinfectant made by combining chlorine with ammonia. | 2.8 mg/LAverageSystem-wide | 4 mg/LMRDL | Within the limit |
Disinfection byproducts
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| HAA5Haloacetic acids — a group of five disinfection byproducts formed when disinfectants react with organic matter. | 37.0625 UG/LAverageDistribution | 60 UG/LMCL | Within the limit |
| TTHMTotal trihalomethanes — a group of four chemicals (including chloroform) formed when chlorine reacts with natural organic matter. | 34.5 UG/LAverageDistribution | 80 UG/LMCL | Within the limit |
| ChlorateA byproduct that can form during disinfection, especially when hypochlorite solutions degrade. | 144 ug/LAverageSFPUC Water | 800 ug/LNL | Within the limit |
| BromoformA trihalomethane disinfection byproduct. | Not detected UG/LHighest single sampleDistribution | None set | None detected |
| BromodichloromethaneA trihalomethane disinfection byproduct. | 2.320625 UG/LAverageDistribution | None set | Detected — no federal limit |
| ChloroformA trihalomethane formed when chlorine reacts with organic matter in water. | 31.9375 UG/LAverageDistribution | None set | Detected — no federal limit |
| DibromochloromethaneA trihalomethane disinfection byproduct. | 0.4371875 UG/LAverageDistribution | None set | Detected — no federal limit |
Inorganic chemicals
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| FluorideA mineral often added to drinking water to help prevent tooth decay. | 0.7 mg/LAverageSystem-wide | 2 mg/LMCL | Within the limit |
| SulfateA naturally occurring mineral from rock and soil. | 18 mg/LAverageSFPUC Water | 500 mg/LMCL | Within the limit |
| ChlorideA naturally occurring salt compound. | 9.3 mg/LAverageSFPUC Water | 500 mg/LMCL | Within the limit |
| NitrateA compound from fertilizer runoff, septic systems, and erosion of natural deposits. | Not detected mg/LAverageSystem-wide | 10 mg/LMCL | Within the limit |
| BromideA naturally occurring salt found in source water. | Not detected ug/LAverageSFPUC Water | None set | Detected — no federal limit |
Physical & aggregate
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| Specific ConductanceA measure of how well water conducts electricity, which tracks dissolved mineral content. | 193AverageSFPUC Water | 1600MCL | Within the limit |
| Total Dissolved SolidsTotal dissolved solids — the combined content of all dissolved minerals and salts. | 102 mg/LAverageSFPUC Water | 1000 mg/LMCL | Within the limit |
| AlkalinityA measure of the water's capacity to neutralize acids. | 60 mg/LAverageSFPUC Water | None set | Detected — no federal limit |
| HardnessA measure of dissolved calcium and magnesium minerals. | 60 mg/LAverageSFPUC Water | None set | Detected — no federal limit |
| pHA measure of how acidic or basic the water is. | 8.9AverageDistribution System-Wide | None set | Detected — no federal limit |
| TOCTotal organic carbon — a measure of organic material dissolved in the water. | 1.5 mg/LAverageSFPUC Water | None set | Detected — no federal limit |
| TurbidityA measure of cloudiness from suspended particles in the water. | 0.4 NTUMaximumSFPUC Water | None set | Detected — no federal limit |
Metals
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| IronA naturally occurring metal common in groundwater. | 14 ug/LAverageSFPUC Water | 300 ug/LMCL | Within the limit |
| BoronA naturally occurring element from rock and soil. | 0.04 mg/LAverageSFPUC Water | 1 mg/LNL | Within the limit |
| Chromium, HexavalentHexavalent chromium ('chromium-6') — the more toxic form of chromium. | 0.1 ug/LAverageSystem-wide | 10 ug/LMCL | Within the limit |
| AluminumA common element sometimes used as a treatment coagulant. | Not detected ug/LAverageSFPUC Water | 200 ug/LMCL | Within the limit |
| CopperA metal that enters water from corroding household plumbing. | Not detected mg/L90th percentileAt the tap | 1.3 mg/LAction level | None detected |
| LeadA toxic metal that leaches into water from old service lines, solder, and plumbing fixtures. | Not detected ug/L90th percentileAt the tap | 15 ug/LAction level | None detected |
| ManganeseA naturally occurring metal from soil and rock. | Not detected ug/LAverageSFPUC Water | 50 ug/LMCL | Within the limit |
| CalciumA naturally occurring mineral that contributes to water hardness. | 15 mg/LAverageSFPUC Water | None set | Detected — no federal limit |
| LithiumA naturally occurring element found in some groundwater. | Not detected mg/LAverageSFPUC Water | None set | Detected — no federal limit |
| MagnesiumA naturally occurring mineral that contributes to water hardness. | 5.7 mg/LAverageSFPUC Water | None set | Detected — no federal limit |
| SilicaA naturally occurring compound from sand and rock. | 7.5 mg/LAverageSFPUC Water | None set | Detected — no federal limit |
| SodiumA naturally occurring salt component. | 16 mg/LAverageSFPUC Water | None set | Detected — no federal limit |
Microbial
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| Escherichia coli (E. coli)Escherichia coli — bacteria found in the gut of humans and animals. | 0MaximumMonthly | 0MCL | None detected |
| Giardia lamblia | 0.02AverageSFPUC Water | 0Public health goal | Detected — no federal limit |
Other
| Contaminant | Measured | Federal limit | Status |
|---|---|---|---|
| Mbaa | Not detected UG/LHighest single sampleDistribution | None set | None detected |
| Dbaa | 0.51875 UG/LAverageDistribution | None set | Detected — no federal limit |
| Dcaa | 22.84375 UG/LAverageDistribution | None set | Detected — no federal limit |
| Mcaa | 1.275 UG/LAverageDistribution | None set | Detected — no federal limit |
| Tcaa | 13.68125 UG/LAverageDistribution | None set | Detected — no federal limit |
Source: California Water Service - San Mateo, CA's 2024 Consumer Confidence Report — the annual drinking-water report every U.S. utility is required to publish. The numbers on this page are the utility's own. A water-quality report covers an entire service area, not a single address.
People also ask about California Water Service - San Mateo, CA's water
+Is California Water Service - San Mateo, CA tap water safe to drink in 2024?
Every one of the 39 contaminants measured in California Water Service - San Mateo, CA's 2024 Consumer Confidence Report is below its federal limit. "Safe" under the EPA's drinking-water standards is health-based, not aesthetic — but by those standards, no measured contaminant in this report exceeds its enforceable threshold. Individual health concerns (e.g. immunocompromised, infant, pregnancy) may warrant additional filtering regardless of compliance.
+What contaminants are in California Water Service - San Mateo, CA tap water?
39 contaminants were measured in California Water Service - San Mateo, CA's 2024 Consumer Confidence Report, spanning metals, disinfection byproducts, and physical & aggregate. 19 have an enforceable federal limit; the rest are detected but unregulated. Every measured value, in the utility's own units, is on this page.
+Where does the data on this page come from?
Every value is transcribed from California Water Service - San Mateo, CA's 2024 Consumer Confidence Report — the annual drinking-water report every U.S. public water utility is required by federal law to publish. The original source document is archived and viewable on this site. A water-quality report covers an entire service area, not a single address.
+How often is California Water Service - San Mateo, CA's water quality data updated?
Each U.S. public water utility publishes one Consumer Confidence Report per year, covering the prior calendar year's measurements. This page reflects the 2024 report; a new report will replace it once the utility publishes its next annual update.
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