Only a small number of Thousand Oaks residents notice a difference in the smell of their tap water when it doesn’t come from the usual supplier.

But many of those who do notice—a handful of sensitive water sniffers—call the city, the water company or the Thousand Oaks Acorn to find out what’s going on.

Recently a reader commented, “The water coming into our home has had a strong smell of bleach and/or chlorine. Even when we run the water through our filtration system, the smell is there. You can also smell the water in the shower.”

He was right. There was a different amount of chlorine in the water. From Dec. 6 through Dec. 13, the primary water supply pipeline used by Calleguas Municipal Water District through Metropolitan Water District of Southern California was shut down to make improvements.

During that service shutdown, water was delivered to Thousand Oaks by the Los Angeles Department of Water and Power through a parallel pipeline that comes with a different disinfecting process.

“It’s unlikely that water users will notice any change in the quality of their tap water; however, as Metropolitan (Water District of Southern California) and (Los Angeles Department of Water and Power) utilize different methods of disinfection, there may be a slight change in taste and odor,” said Dr. Don Kendall, Calleguas general manager.

Such a switch happens at least once a year, sometimes more often, and when it does, the city gets fewer than five calls asking, “What’s going on?” said Mark Watkins, Thousand Oaks public works director.

Calleguas’ water supply from Los Angeles was safe and reliable and met all federal and state water quality standards, Kendall said.

Calleguas is one of 26 member agencies of the Metropolitan Water District of Southern California and the primary water supplier for Thousand Oaks and much of Ventura County, providing water service to a population exceeding 550,000. Through 22 retail water agencies and companies, Calleguas provides water to the cities of Oxnard, Camarillo, Moorpark, Simi Valley, Thousand Oaks and Port Hueneme, as well as surrounding unincorporated areas.

There’s no difference in the water other than the disinfectant process.

“One comes from snowpack from the east side of the Sierra Mountains and the other from snow pack from the west side,” Watkins said.