We continue to hear that Hetch Hetchy Valley shouldn’t be restored because San Francisco’s water quality is exceptional. We have never believed this argument, but now we have evidence to back up our claim that San Francisco’s water quality, while good, is not truly special.
If you’re feeling a sense of déjà vu, you’re right – we wrote about this last November. We apologize for being repetitive, but this is an important message that bears repeating. Something that San Francisco officials and residents alike, as well as their wholesale customers need to hear. We will be sharing this information broadly and ask our supporters to do the same.
We are grateful to the University of Colorado Capstone Team for designing and initiating the taste test. And we are happy to collaborate with San Francisco or other parties who feel more research is warranted.
We are comfortable, however, with the results – that 75% of respondents favored either East Bay or Marin water over San Francisco water. The Bay Area Water Taste Test report. is included below and posted online. The complete report, with its five appendices, is posted online as well. Again, please share.
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Bay Area Water Taste Test
Restore Hetch Hetchy
July 2025
Overview
Restore Hetch Hetchy is committed to restoring the Hetch Hetchy Valley in Yosemite National Park while ensuring continued water and power reliability for all communities that rely on the Tuolumne River.
Some opponents and skeptics of restoration have asserted that the quality of San Francisco’s water is exceptional, and that the City’s residents and customers will be forced to drink inferior water when Hetch Hetchy Reservoir is relocated and Tuolumne River supplies are diverted from other locations.
Restore Hetch Hetchy agrees that San Francisco’s water is high quality, and we maintain it will still be good when Hetch Hetchy Valley is restored. We believe residents will experience no noticeable difference in water quality.
To test this assumption, we conducted taste comparisons between San Francisco’s water and other high-quality local supplies from the East Bay and Marin County. The results confirmed our expectations.
In a series of double blind taste tests, most respondents actually preferred East Bay and Marin water to San Francisco water. These findings indicate that water quality should not be a primary concern in debates over restoring the Hetch Hetchy Valley in Yosemite National Park.
Summary
In 2024, Restore Hetch Hetchy retained graduate students from the University of Colorado through its Capstone Program to design and initiate a double-blind water taste test to evaluate preferences of Bay Area residents.
In a series of trials conducted between June and October, the Capstone Team and Restore Hetch Hetchy asked participants to compare water supplies delivered by the San Francisco Public Utilities Commission (SFPUC, often colloquially called “Hetch Hetchy” water) with supplies delivered by the East Bay Municipal Utilities District (EBMUD) and the Marin Municipal Water District (MMWD). Participants ranked the taste of the three sources based on personal preference, with ties permitted.
A majority of participants preferred the taste of East Bay or Marin water to that of San Francisco. Out of 114 first place votes, 47 people (41%) selected East Bay water as best, 39 people (34%) selected Marin water as best, and 28 people (25%) selected San Francisco water as best. The results challenge the perception that ‘Hetch Hetchy’ water is superior. See Figure 1.
Methodology
The taste test took place in 3 phases:
- In June, samples were collected at the SFPUC and EBMUD headquarters and from a Mexican restaurant in Larkspur (staff at the MMWD declined to provide samples for the test.). The University of Colorado Capstone Team, who designed the test, collected the opinions of passersby at the Rockridge BART station in Oakland. The Capstone Team’s Findings and their Methodology and Recommendations are included as Appendices A and B.
- In July, samples were collected from private homes in San Mateo County (90% SFPUC water), Oakland (EBMUD) and Fairfax (Marin). The samples were offered to passersby at Safeway in Oakland and in private homes. These samples were also sent to Tap Score, an independent lab, for detailed analysis (see Appendices C (SFPUC), D (EBMUD) & E (MMWD).
- In October, samples were collected from the same private homes in San Mateo County, Oakland and Fairfax. The water was offered to people attending Restore Hetch Hetchy’s Annual dinner on October 26 – as soon as they arrived and before they consumed any other food or beverage.
All testing followed a double-blind protocol: neither tasters nor test administrators knew which sample came from which source. Further, all taps were flushed before filling glass bottles, and all samples were kept at room temperature.
Testing and Results
A breakdown of the results from the separate trials reflecting the variability of responses is provided in Figure 2. Note that the exact mix of sources in any utility’s supply varies over time and location.[1]
Discussion
There are two fundamentally important aspects of water quality – health and taste. California’s large cities are fortunate that professional water agency staff regularly test and treat supplies, ensuring that their water is safe to drink.[2]
Water delivered in Marin, the East Bay and San Francisco is not only safe, but tastes good due to its modest mineral content. Water supplies in the East Bay and San Francisco primarily originate in the Sierra Nevada and are augmented by local rainfall and small amounts of groundwater. Water supplies in Marin come from local rainfall and groundwater, some of which is imported from Sonoma County.
Some water experts have indicated they prefer San Francisco’s water for its “pure” taste. Others prefer water with a slight mineral taste (mostly calcium and magnesium), suggesting that San Francisco’s water may be too neutral for their palate. Too much mineral content, as is the case with much of southern California’s water, is generally disfavored. Figure 3, below, compares the mineral content of the samples used in the taste tests with values reported in water supplies for San Diego, Los Angeles and Sacramento.
Conclusion
When Hetch Hetchy Valley is restored, San Francisco will still rely principally on the Tuolumne River for the majority of its supply. Water will be stored in and diverted from Cherry, Eleanor and/or Don Pedro Reservoirs – with mineral content perhaps similar to EBMUD’s Pardee Reservoir. Customers may like their water even better!
Restore Hetch Hetchy believes the reputation of ‘Hetch Hetchy’ water is overstated. We welcome opportunities to collaborate with the San Francisco Public Utilities Commission or other interested parties on future independent testing.
[1] On average, San Francisco derives 85% of its supply from the Tuolumne River. In recent years, however, the City has relied on local supplies and reservoirs in winter months so staff can do maintenance on the Mountain Tunnel – something customers rarely notice.
[2] Water in many small communities in California is not in fact safe to drink. See the Community Water Center for more information.