Cupertino, California

Cupertino, California Cupertino, California

What is the Water Quality in Cupertino, California?

[Updated: June 9, 2023]

Compared to other US cities, Cupertino water quality ranks in the lower range for contamination excluding Lead.

Most of their 16 contaminants have cancer-causing attributes.

  • Haloacetic acids (HAA5) are at extremely high levels: 272x health guidelines.
  • Haloacetic acids (HAA9) are at extremely high levels: 509x health guidelines.
    • HAA5 and HAA9 are byproducts of chlorine treatment, a common method of disinfecting water supplies.

Let’s look closer at what’s in Cupertino water.

What’s in Cupertino water?

Here are the top 5 chemical compounds in your water and what health issues they can potentially cause:

  1. Hexavalent Chromium – Potential effect: Cancer
  2. Haloacetic acids (HAA5) – Potential effect: Cancer
  3. Nitrate – Potential effect: Cancer
  4. Nitrate and nitrite – Potential effect: Cancer
  5. Total trihalomethanes – Potential effect: Cancer

These are five of the 16 contaminants analyzed by the Environmental Working Group (

6 of these contaminants are rated as exceeding EWG Health Guidelines.

Does Cupertino have Lead contamination?

No, Cupertino does not currently have lead in its water. The most recent Lead samples collected from 2015 through 2017 showed concentrations of 0.0 parts per billion (ppb).

The legal limit for lead is 15 parts per billion. Being well-below this level is a good thing.

  • Concentrations between 3.8 ppb and 15 ppb put a formula-fed baby at risk of elevated blood lead levels. Read more about the symptoms of Lead in water.

There is no safe level of lead for humans.

  • The good news is that 99.99% of the lead can be filtered out.

See the What Can You Do? section below to learn how to filter out contaminants.

Where does Cupertino’s water come from?

Cupertino’s water comes from the Calabazas Creek – Frontal San Francisco Bay watershed.

All 4 water sources in the Calabazas Creek – Frontal San Francisco Bay watershed are in Impaired condition. These are:

  • Calabazas Creek (Santa Clara County)
  • Guadalupe Slough
  • Stevens Creek
  • Stevens Creek Reservoir

Ideally, a water source would be rated in Good condition.

Learn more from How’s My Waterway

See below for what you can do to improve Cupertino’s water.

Conclusion – What Can You Do?

Information about water quality in Cupertino can be surprising.

But there are things you can do in your home to clean up your water.

To Remove Lead and Other Contaminants In Your Home:

  • Use Activated Carbon filters to remove most contaminants in your drinking water.
    • Faucet-mount filters work better than pitchers.
    • PUR and Brita are low-cost and effective.
Brita Lead Filtration
Brita Faucet Mount – Amazon
  • To filter out even more contaminants, consider a Reverse Osmosis water filtration system for your house.
    • These are more expensive than pitchers to purchase, but are much more effective.
    • They have the benefit of filtering out heavy hitters like:
      • 1,4-Dioxane – irritating to eyes and respiratory tract. May cause damage to the central nervous system, liver, and kidneys.
      • Aluminum
      • Barium
      • Fluoride
      • Haloacetic acids (HAA5) – byproduct of chlorination
      • Haloacetic acids (HAA9) – byproduct of chlorination
      • Hexavalent chromium
      • Molybdenum
      • Nitrate
      • Nitrite
      • Strontium – Can lead to bone growth problems in children.
      • Total trihalomethanes – byproduct of chlorination
    • Our recommendation: APEC Reverse Osmosis Systems
Reverse Osmosis Systems for Cupertino
APEC system – Amazon

In Your Community:

Contact your local government officials and put pressure on them to invest in cleaner waterways and upgraded city water filtration and treatment.

Go to: to find contact information for your local officials.

Water Quality in Other California Cities

California Water Quality Page

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