San Francisco water officials have located the source of a harmless chemical that gave drinking water in The City a funny taste and odor this week.

When operators with the San Francisco Public Utilities Commission last week changed the source of some of the drinking water consumed by the agency’s 2.6 million customers, an aromatic compound called geosmin lingered in the water and was somehow not flushed out when the water was treated at the Sunol Valley Water Treatment Plant.

That chemical is believed to have originated in the San Antonio Reservoir, which the SFPUC began drawing from prior to the first reports of a funny odor or taste in the water on Dec. 2, said Steve Ritchie, the SFPUC’s assistant general manager for water.

About 85 percent of the drinking water consumed by SFPUC customers comes from the Hetch Hetchy Reservoir, and the agency receives the remaining 15 percent from five other Bay Area reservoirs on a rotating basis.

To mitigate the funny odor and taste, the SFPUC is switching to a reservoir on the Peninsula as a drinking water source and expects the issue to dissipate within a week.

Ritchie emphasized the water is safe to drink.