POST FALLS — Chlorination of the Post Falls water distribution system began this week as part of its annual maintenance. 

The goal is to keep chlorine residuals above 0.25 parts per million for 30 days. The EPA enforces a maximum level of 4.0 ppm chlorine in drinking water. 

Post Falls staff typically time the chlorination program to run when the city experiences a reduction in pumping demands.  

Utilities manager Craig Borrenpohl said city staff perform regular tests of the chlorine concentration to adjust levels as necessary to keep an effective dose while minimizing less-pleasant side effects.   

"The main concern we hear from customers relates to the taste and odor,” Borrenpohl said. 

The seasonal chlorination helps protect the Post Falls water system.      

The city typically notifies customers about the fall chlorination schedule in the August or September bill and on social media prior to chlorination.  

“Post Falls is fortunate to have the Rathdrum Prairie Aquifer as a safe and reliable source of drinking water,” Borrenpohl said. “Because we have such a high-quality of source water, continuous treatment is not required year-round.”   

Kyle Marine, Coeur d'Alene water department director, said the city does not conduct a fall chlorination program 

"Our system is set up to continuously inject a low dose of Cl2 (chlorine gas) at all times to keep a residual of .02," he wrote.

When water customers winterize their irrigation system by blowing out sprinkler systems, the activity poses a risk to the drinking water distribution system.  

Backflow prevention devices are required on irrigation systems to ensure water can't flow from a customer’s connection back into the drinking water distribution mains. A missing or malfunctioning backflow prevention device could allow for contamination from a sprinkler blowout.  

Chlorination also helps reduce organic biofilms, which can build up on the inside of the water mains if not regularly controlled, Borrenpohl said.  

“Disinfecting the system via the addition of chlorine has been shown to be a safe and effective means of reducing the risk of bacterial contamination,” Borrenpohl said. “Completion of our annual chlorination while a majority of sprinkler blow-outs occur helps ensure we’re being protective of the system when it is most at risk.”  

City staff recommend individuals consult their physicians to discuss specific health concerns related to chlorine in the drinking water.  

For more information or to be added to the email notification list, contact [email protected].