# Tesoro Viejo Master Mwc, Inc. — San Jose, Ca, CA — Drinking Water Quality (2023)

> Contaminant levels for the Tesoro Viejo Master Mwc, Inc. — San Jose, Ca, CA public water system from its 2023 Consumer Confidence Report, compared to federal limits.

- Page: https://www.thewatermap.com/water/ca/tesoro-viejo-master-mwc-inc-san-jose-ca/2023
- JSON API: https://www.thewatermap.com/api/water/ca/tesoro-viejo-master-mwc-inc-san-jose-ca/2023
- Source: the utility's annual Consumer Confidence Report (CCR)
- Verification: transcribed by a model, cross-checked by a second model, approved before publishing
- Reporting year: 2023
- Contaminants measured: 15
- Contaminants with a federal limit: 3
- Contaminants at or above the federal limit: 0
- Part of The Water Map — https://www.thewatermap.com

## Contaminants measured

| Contaminant | Category | Measured level | Sampling context | Federal limit | Status |
|---|---|---|---|---|---|
| HAA5 | Disinfection byproducts | 46 ug/L (Average) | Annual Average | No federal limit | Within the limit |
| NDMA | Disinfection byproducts | 3.1 ng/L (Average) | System-wide | 10 ng/L (NL) | Detected — no federal limit |
| TTHM | Disinfection byproducts | 66 ug/L (Average) | Annual Average | No federal limit | Approaching the limit |
| Aluminum | Metals | 24 ug/L (Average) | System-wide | No federal limit | Detected — no federal limit |
| Calcium | Metals | 3.3–22 mg/L (Range) | System-wide | No federal limit | Detected — no federal limit |
| Copper | Metals | 0.19 mg/L (90th percentile) | At the tap | 1.3 mg/L (Action level) | Within the limit |
| Lead | Metals | Not detected ug/L (90th percentile) | At the tap | No federal limit | None detected |
| Magnesium | Metals | 0.67–1.2 mg/L (Range) | System-wide | No federal limit | Detected — no federal limit |
| Sodium | Metals | 3.6–5.6 mg/L (Range) | System-wide | No federal limit | Detected — no federal limit |
| Escherichia coli (E. coli) | Microbial | 0 (Maximum) | Monthly | No federal limit | None detected |
| Chlorine Free | Other | 1.6 mg/L (Average) | System-wide | 4 mg/L (MCL) | Within the limit |
| Alkalinity | Physical & aggregate | 14–60 mg/L (Range) | System-wide | No federal limit | Detected — no federal limit |
| Hardness | Physical & aggregate | 11–58 mg/L (Range) | System-wide | No federal limit | Detected — no federal limit |
| pH | Physical & aggregate | 6.7–8.5 (Range) | System-wide | No federal limit | Detected — no federal limit |
| Toluene | VOCs & pesticides | Not detected ug/L (Average) | System-wide | No federal limit | Within the limit |

## What these contaminants are

- **HAA5** — Haloacetic acids — a group of five disinfection byproducts formed when disinfectants react with organic matter. Long-term exposure above the federal limit is associated with an increased cancer risk.
- **TTHM** — Total trihalomethanes — a group of four chemicals (including chloroform) formed when chlorine reacts with natural organic matter. Long-term exposure above the federal limit is linked to liver, kidney, and central-nervous-system effects and increased cancer risk.
- **Aluminum** — A common element sometimes used as a treatment coagulant. Regulated only as a secondary (cosmetic) standard; high levels can discolor water.
- **Calcium** — A naturally occurring mineral that contributes to water hardness. Not federally regulated for health; affects scaling and taste.
- **Copper** — A metal that enters water from corroding household plumbing. Short-term exposure causes stomach distress; long-term exposure can damage the liver and kidneys.
- **Lead** — A toxic metal that leaches into water from old service lines, solder, and plumbing fixtures. There is no safe level of lead; it harms brain development in children and raises blood pressure in adults. The EPA sets an action level, not a health goal above zero.
- **Magnesium** — A naturally occurring mineral that contributes to water hardness. Not federally regulated for health; affects scaling and taste.
- **Sodium** — A naturally occurring salt component. Not federally regulated for health; relevant for people on sodium-restricted diets.
- **Escherichia coli (E. coli)** — Escherichia coli — bacteria found in the gut of humans and animals. Its presence in drinking water indicates fecal contamination and a real risk of waterborne illness.
- **Alkalinity** — A measure of the water's capacity to neutralize acids. Not federally regulated for health; relevant to corrosion control and treatment.
- **Hardness** — A measure of dissolved calcium and magnesium minerals. Not federally regulated for health; affects scaling, soap use, and taste.
- **pH** — A measure of how acidic or basic the water is. Regulated only as a secondary standard; very low or high pH can corrode pipes or affect taste.

## How to read this

- A water-quality report covers an entire service area, not a single address.
- 'Federal limit' is the EPA standard (MCL, action level, treatment technique, etc.) that the measured level is compared against.
- 'At or above the federal limit' means the utility's own reported figure met or exceeded that standard.

_Figures are the utility's own published numbers. Generated 2026-06-04 from thewatermap.com._