Which chemical is commonly used to treat water in the tower?

• A. Bleach
• B. Hydrochloric acid
• C. Ammonia
• D. Sodium hydroxide

Answer: (A)

Disinfection and maintaining a sanitary water system is the key idea here. Water held in a tower needs to be kept free of bacteria and algae, and it’s important to have ongoing protection against recontamination. Bleach, a chlorine-based disinfectant, is ideal for this because it rapidly kills microbes and leaves a residual sanitizing level in the water. That residual helps prevent new growth while the water sits in the tower or moves through the system. It’s also practical—effective across a range of conditions, easy to dose, and cost-effective—making it the most commonly used treatment for towers.

The other options have different roles. Hydrochloric acid is mainly for pH adjustment and scale control, not disinfection. Ammonia is not a sanitizer by itself (though it can be used in combination with chlorine to form chloramines, that’s a distinct treatment approach). Sodium hydroxide is another pH/alkalinity adjuster and corrosion control agent, not a disinfectant.