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  • Writer's pictureKevin Peterson

Is Your Tap Water Trustworthy? Investigating the Quality of SF Bay Area's Water Supply

Updated: Dec 15, 2023

Living in the United States (and in California), we should not have to worry about contaminated water, right? In this blog, I'll show you the data and what actionable steps you can take to address any health concerns related to water.

Who sets the SF Bay Area water quality standards?

Water standards are federally regulated and governed by the Enviromental Protection Agency (EPA), and the state of California via the California Public Utilities Commission (CPUC).

Are there issues with these standards?

Significant research conducted by an independent 3rd party called has discovered two troubling data points.

  1. Communities served by smaller water systems tend to have a greater cancer risk

  2. Although tap water may met federal drinking water standards, more than 20 carcinogens could still be found in our water which has been linked to over 100,000 cases of cancer.

The first point is less of a worry here in the San Francisco Bay Area after I saw that the regulated water companies here all service more than 10K customers. For a full list of water providers in California, click here.

SF Bay Area water quality regulated water companies

This Cal Water Quality Report below also shows what systems are currently incompliance, out of compliance, or returned t compliance. All in the Bay Area are good for now...

SF Bay Area water quality compliance map

What is the quality of our water?

When looking at the EWG website, I see the following for the city of San Mateo - NINE contaminants are in our water at what looks to be very unhealthy levels:

SF Bay Area water quality contaminants

How do I find my own SF Bay Area water quality?

Click here and you will be sent directly to the EWG website.

Those numbers are disturbing but thankfully, activated carbon such as a Brita water filter reduces (but does not eliminate) all of the above. The only exception is Chromium (hexavalent) which requires an ion exchange system.

SF Bay Area water quality contaminant reduction options

Why Are The (SF Bay Area) Water Quality Standards Behind?

A few reasons, namely:

  • There is not enough funding to help replace lead pipelines and clean up our drinking water, i.e. Flint Michigan.

  • Federal water safety standards aren’t keeping pace with the latest science on contaminants – some regulations haven’t been updated in more than 50 years, and the Environmental Protection Agency is not moving fast enough on new drinking water rules.

What about Polyfluoroalkyl substances (PFAS)?

California has cracked down in recent years on PFAS in many consumer goods like carpets, toys and makeup, but drinking water is of particular importance because consuming PFAS by mouth may be more harmful than touching by skin through clothing, for instance. One 2020 study found that more than 200 million Americans are likely exposed to some PFAS in drinking water.

The Bay Area’s drinking water generally has low levels of PFAS because large water systems in the region get most of their drinking water from pristine sources in the Sierra, i.e. Hetch-Hetchy project, or local reservoirs in regional parks, according to researchers who study toxic chemicals in drinking water.

SF Bay Area water quality drinking from Hetch Hetchy
The aqueduct delivers an average of 265,000 acre⋅ft (327,000,000 m3) of water each year, or 31,900,000 cu ft (900,000 m3) per day, to residents of San Francisco and San Mateo, Santa Clara and Alameda Counties

Water from Hetch Hetchy is among the cleanest municipal water in the United States. As such, San Francisco is one of six U.S. cities not required by law to filter its tap water, although the water is disinfected by ozonation and, since 2011, exposure to UV. The water quality is high because of the unique geology of the upper Tuolumne River drainage basin, which consists mostly of bare granite. And as a result, the rivers feeding Hetch Hetchy Reservoir have extremely low loads of sediments and nutrients.

BONUS: What is hard water?

Hard water does not pose a health risk, and there is no health-based drinking water standard.

Although hardness does not affect the safety of your water, it can cause aesthetic issues. Hard water can:

  • Affect the taste of your water, sometimes described as metallic or medicinal because of naturally occurring iron and minerals in the groundwater

  • Build up on dishes, glasses, plumbing fixtures, and wash basins

  • May cause poor soap and detergent performance

  • Build-up of scale on pipes and fixtures that can eventually lead to lower water pressure and reduced efficiency of water heaters.

Action items you may want to consider for hard water?

Consider installin a water softener or ion exchange system.

  • These systems can increase the sodium content of your water, which may pose health concerns for your household.

  • These systems may also contribute additional salts to wastewater treatment plants and ultimately to recycled water, which is reused for other purposes.

  • If you want to avoid the use of water softeners or ion exchange systems for health or environmental reasons, there are cleaning products and natural remedies (such as vinegar) that will help to address mineral build-up caused by hard water.

Action items you may want to consider for drinking more healthy water?

  • Consider getting a drinking water filter (carbon or reverse osmosis)

  • Talk to your state and local government representatives to voice your concerns.

In a future blog, let me know if you'd like a deep dive into the water quality of wells and groundwater in the SF Bay Area.


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