SAN FRANCISCO—According to reports, residents in San Francisco and other cities including Palo Alto reported odd tastes and smells coming from their tap water. Some of residents took to social media sites to report the smell and taste similar to “pond weed” or “lake water.” Residents of Hayes Valley, Potrero Hill, Noe Valley, and the Richmond and Mission Districts of San Francisco commented on Reddit that their water also tasted strange.

According to Charles Sheehan, a representative for the San Francisco Public Utilities Commission (SFPUC), Hetch Hetchy Valley, located in the northwestern region of Yosemite, has been cited as the cause of the tap water issues, where it blends water from other sources.

Sheehan shared with SF Gate that the SFPUC had shifted gears, that they had “reduced the supply from one part of our system and increased the supply from another part of our system.”

Palo Alto Online reported that residents of the area, which the SFPUC supplies Hetch Hetchy water have been complaining about the unpleasant water taste. According to their site, the complaints began on November 29.

Catherine Elvert, a representative for the city of Palo Alto Utilities indicated that the SFPUC had reduced the amount of its primary Hetch Hetchy water from 145 million gallons per day to 105 million and blended it with water from the Sunol Valley Water Treatment Plant.

The SFPUC had not pre-warned San Francisco residents that the water could develop an unpleasant smell or taste. The city of Palo Alto Utilities questioned the SFPUC about the potential harmful substances in the water. Elvert noted that the quantity of organic matter including sediments and algae is higher in the newer supply, but that “treatment eradicates any potential pathogens.”

Sheehan noted that the city’s water supply generally consists of about 85 percent Hetch Hetchy water. Despite the shift, Sheehan, Elvert, and other officials have assured the public that the taste and smell of the cities’ tap water should improve over the course of the next few days.