Funky-Smelling Tap Water Temporary, Due To Seasonal Temperature Change: Manassas City

MANASSAS, VA – The City of Manassas has responded to reports of unusual tastes or odors in residents' tap water, saying the changes result from naturally occurring compounds in the city's natural water source.

"If you have recently noticed a different taste and odor in your tap water, it is being caused by changes in Lake Manassas, the City's water source, which also supplies water to parts of Prince William County," the city wrote in a social media announcement. "Tests showed slightly higher concentrations of Geosmin and Methyl-Isoborneol (MIB)—which are naturally occurring compounds—in Lake Manassas. Both compounds can give your water an earthy/musty taste and odor, but do not pose a public health risk."

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Some residents had noted a new odor on social media.

The city says levels of those compounds fluctuate with changing temperatures and the smells generally emerge twice a year. "When it gets colder or warmer, lake water moves from top to bottom and stirs up natural compounds. The Water Department is working to reduce the taste and odor, and always monitors the water supply and finished water for these and other compounds."

Both compounds are produced by microorganisms present in water, including some blue-green algae. A Smithsonian Magazine article calls Geosmin "the smell of rain."

Multiple papers discuss ways of mitigating the compounds' effects on the taste and smell of water, because they're a common source of complaints about water quality, and some people are able to detect their presence in minuscule amounts.