City of Madison Logo
Image: Water Header

Water Treatment: Chlorine and Fluoride
Image: At Your Service

Last updated:  9/10/07

Disinfection:
Chlorine is used to disinfect our water and minimize the risk of microbial contamination by bacteria or viruses. The average free residual chlorine concentration in the system is maintained at 0.3 parts per million (ppm) (also stated as milligrams per liter, mg/L).

The utility is required to maintain chlorine levels as water is pumped from the wells as close as possible to 0.3 mg/L, and to take action to remove a well from service if chlorine levels go below 0.15 mg/L.   Levels at or above 0.1 mg/L continue to be the goal for water throughout the distribution system.  Corrective action would be taken if chlorine levels of water leaving a well were to exceed 0.55 mg/L, and a well would be shut down if levels exceed 4.0 mg/L.

Chlorine is added to drinking water systems to assure that microbial organisms such as bacteria and viruses cannot survive in the water.  Some customers may notice an increase in the smell or taste of chlorine in the water when levels are initially raised. The chlorine levels are not a health concern and, in fact, are established to prevent health risk from bacteria and viruses.  New chlorine levels at the wells have been phased in.  If customers experience a persistent and excessive odor or taste of chlorine in their drinking water, they should call the utility at 266-4654, and the report will be investigated

Fluoridation:
Fluoride is added to our water to improve dental health and reduce tooth decay. The average fluoride level in our water is 1.1 parts per million.

Monitoring:
Daily samples are taken for some testing and other regular sampling programs test water in the distribution system. Chlorine and fluoride levels are adjusted as necessary to ensure safe water is delivered to the tap.