What is the purpose of the Final Flushing step in the water main disinfection process?

• A. To restore water pressure
• B. To mix residual disinfectant uniformly
• C. To remove heavily chlorinated water until the concentration is acceptable for domestic use
• D. To cap the main and perform sampling

Answer: (C)

Final Flushing is about purging the distribution main of the heavily chlorinated water that’s used during disinfection so the water leaving the main has an acceptable residual chlorine level for domestic use. After injecting a strong disinfectant, you flush the line to remove excess chlorine and any loosened debris, ensuring the water supply meets safety and taste/odor standards before customers receive it. The other options don’t capture the main purpose: restoring pressure is not the primary objective of this step, mixing residual disinfectant uniformly happens as water flows but isn’t the goal of flushing, and capping the main to perform sampling isn’t how you conduct or justify the flush.