A $14 million three year contract for the purchase of bleach was approved by the Board of Supervisors Tuesday, after gaining a lot of attention.

The San Francisco Examiner first reported the interesting fact that most people probably weren’t aware of, that the San Francisco Public Utilities Commission pours bleach down the sewer to get rid of the stink, described as a smelly egg odor.

About 20 percent of the bleach purchased will be put down the sewers, the agency announced following The Examiner’s report. At the time of the article, the agency was unable to provide how much would be poured into the sewer system.

Also, the agency said that water conservation efforts were contributing to the smell, since the sewer system relies on water flow to move the sewage to the treatment plants.

“The consumption of water has decreased significantly. We are having a difficult time having enough water to convey the material to the treatment plants,” said Tommy Moala, assistant general manager for the SFPUC.

Following another media report that places the blame of water conservation on low-flow toilets, the SFPUC released a statement defending low-flow toilets and other efforts, but also saying the low-flow devices  should not take all the blame.

“Recent media reports that cited low-flow toilets as the sole cause of odors in San Francisco’s sewage pipelines are misleading,” the statement says. “Sewer odors occur for a variety of reasons and will always represent a challenge for wastewater utilities. Whether odors are caused by engineering design issues or flow patterns, they must not become a clarion call to stop water conservation efforts. Instead they should become part of the long-term capital and operational planning discussion for every utility.”

jsabatini@sfexaminer.com