What is the minimum level of free chlorine used during the hyperchlorination process?

The minimum level of free chlorine used during the hyperchlorination process is crucial for effectively controlling Legionella and ensuring the safety of water systems. The correct answer reflects the recommended concentration necessary to achieve a significant level of disinfection.

Hyperchlorination is a shock treatment applied to plumbing systems that allows for a higher concentration of chlorine to effectively eliminate biofilms and reduce bacterial colonies, including Legionella. The concentration of 20 parts per million is considered adequate to penetrate and disinfect biofilms, as well as to maintain efficacy against pathogens in the water for a sufficient duration.

Using this level allows for a balance between effectiveness in disinfection and the potential for corrosion or other negative effects that can occur at higher concentrations. Therefore, the recommendation to use 20 parts per million of free chlorine ensures that water systems remain safe and compliant with health standards while minimizing the risk of water quality deterioration.