Bad Taste in Your Mouth? It’s Just Your Tap Water, Again

Blooming algae has given Marin tap water a weird taste for the second time this summer.


More algae has starting blooming at Nicasio Reservoir, giving water a swampy taste for some living in San Anselmo and Fairfax. 

Tap water for some residents.

While the water was perfectly harmless, Marin Municipal Water District Officials treated the water with copper sulfate and the taste went away in a few days.

But the taste is back.

MMWD spokesperson Libby Pischel confirmed Wednesday the weird taste has the same culprit – blooming algae. The earthy taste is caused by a naturally occurring compound called geosmin, which is released when algae blooms, according to Pischel. 

“The water was being treated today and yesterday. This should be the last time," Pischel said. "We apologize for any inconvenience or concern on the part of our customers."

The Nicasio Reservoir feeds the San Geronimo treatment plant, which serves San Geronimo Valley, Ross Valley (including San Anselmo and Fairfax) and some of San Rafael.

Pischel said in Sepember the treatment plant will start getting water from other Marin reservoirs. The system can easily blend water from different reservoirs (such as combining water from Kent Lake and Nicasio), but water from Bon Tempe usually feeds Southern Marin, Pischel said.

Do you get worried about drinking tap water? Vote in our poll below. Of the roughly 30 Patch readers who have participated by Aug. 22, . Some readers, though, are more concerned about drinking tap water, including . 


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