# City of Cupertino, CA — Drinking Water Quality (2024)

> Contaminant levels for the City of Cupertino, CA public water system from its 2024 Consumer Confidence Report, compared to federal limits.

- Page: https://www.thewatermap.com/water/ca/cupertino/2024
- JSON API: https://www.thewatermap.com/api/water/ca/cupertino/2024
- 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: 2024
- Contaminants measured: 20
- Contaminants with a federal limit: 17
- 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 |
|---|---|---|---|---|---|
| Chlorine | Disinfectants | 1.17 mg/L (Running annual avg) | System-wide | 4 mg/L (MRDL) | Within the limit |
| Bromate | Disinfection byproducts | 1.7 ug/L (Average) | VW Surface Water | 10 ug/L (MCL) | Within the limit |
| HAA5 | Disinfection byproducts | 35.8 ug/L (Average) | Site Average | 60 ug/L (MCL) | Within the limit |
| TTHM | Disinfection byproducts | 76.96 ug/L (Average) | Site Average | 80 ug/L (MCL) | Approaching the limit |
| Fluoride | Inorganic chemicals | 0.8 mg/L (Average) | VW Surface Water | 2 mg/L (MCL) | Within the limit |
| Nitrate | Inorganic chemicals | 3 mg/L (Average) | Groundwater | 10 mg/L (MCL) | Within the limit |
| Aluminum | Metals | Not detected mg/L (Average) | VW Surface Water | 1 mg/L (MCL) | Within the limit |
| Arsenic | Metals | Not detected ug/L (Average) | Mountain Surface Water | 10 ug/L (MCL) | Within the limit |
| Barium | Metals | 0.18 mg/L (Average) | Groundwater | 1 mg/L (MCL) | Within the limit |
| Chromium, Total | Metals | 3.2 ug/L (Average) | Groundwater | 10 ug/L (MCL) | Within the limit |
| Copper | Metals | 0.23 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 | 15 ug/L (Action level) | None detected |
| Selenium | Metals | Not detected ug/L (Average) | Mountain Surface Water | 50 ug/L (MCL) | None detected |
| Cryptosporidium | Microbial | Not detected (Average) | Mountain Surface Water | No federal limit | Detected — no federal limit |
| Giardia lamblia | Microbial | 0.22 (Average) | Mountain Surface Water | No federal limit | Detected — no federal limit |
| Total Coliform | Microbial | 0.13 % (Average) | System-wide | 0 % (MCLG) | Detected — no federal limit |
| Turbidity | Physical & aggregate | 0.9 NTU (Average) | Groundwater | No federal limit | Detected — no federal limit |
| Combined Radium | Radionuclides | Not detected pCi/L (Average) | Groundwater | 5 pCi/L (MCL) | Within the limit |
| Gross Alpha | Radionuclides | 3.3 pCi/L (Average) | VW Surface Water | 15 pCi/L (MCL) | Within the limit |
| Uranium | Radionuclides | 1.3 pCi/L (Average) | VW Surface Water | 20 pCi/L (MCL) | Within the limit |

## What these contaminants are

- **Chlorine** — A disinfectant added to drinking water to kill bacteria and viruses. Effective and necessary, but high residual levels can cause taste and odor issues; the EPA caps the residual disinfectant level.
- **Bromate** — A disinfection byproduct formed when bromide-containing water is treated with ozone. Classified as a probable human carcinogen; the EPA sets a strict maximum contaminant level.
- **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.
- **Fluoride** — A mineral often added to drinking water to help prevent tooth decay. Beneficial at low levels, but long-term exposure above the federal limit can cause bone disease and tooth mottling.
- **Nitrate** — A compound from fertilizer runoff, septic systems, and erosion of natural deposits. Levels above the federal limit can cause 'blue baby syndrome,' a serious oxygen-transport condition in infants.
- **Aluminum** — A common element sometimes used as a treatment coagulant. Regulated only as a secondary (cosmetic) standard; high levels can discolor water.
- **Arsenic** — A naturally occurring element that also enters water from industry and agriculture. A known human carcinogen; long-term exposure is linked to skin, bladder, and lung cancer.
- **Barium** — A metal from erosion of natural deposits and industrial discharge. Long-term exposure above the federal limit can raise blood pressure.
- **Chromium, Total** — Total chromium — the sum of all chromium forms, from natural deposits and industrial discharge. Long-term exposure above the federal limit can cause allergic dermatitis; includes hexavalent chromium.
- **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.
- **Selenium** — A trace element from natural deposits and industrial discharge. Essential in tiny amounts, but long-term exposure above the federal limit can cause hair and fingernail loss and circulatory problems.
- **Total Coliform** — A group of bacteria used as an indicator of overall water-system sanitation. Coliforms themselves are usually harmless, but their presence signals that disease-causing organisms could enter the system.
- **Turbidity** — A measure of cloudiness from suspended particles in the water. High turbidity can shelter microbes from disinfection; the EPA enforces it through a treatment-technique standard.
- **Combined Radium** — Combined radium-226 and radium-228 — naturally occurring radioactive elements. Long-term exposure above the federal limit increases the risk of bone cancer.
- **Gross Alpha** — Gross alpha particle activity — a combined measure of alpha-emitting radioactive substances. Long-term exposure above the federal limit increases cancer risk.
- **Uranium** — A naturally occurring radioactive metal from erosion of natural deposits. Long-term exposure above the federal limit can damage the kidneys and increase cancer risk.

## 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 2026-05-25 from thewatermap.com._