When disinfecting storage facilities using the chlorinate and fill method, how long should the chlorinated water stay in contact with the storage facility before filling it all the way?

• A. 2 Hours
• B. 12 Hours
• C. 24 Hours
• D. 6 Hours

Answer: (D)

Chlorination needs time to work. In the chlorinate and fill method, the water must stay in contact with the disinfectant long enough for chlorine to inactivate microbes on surfaces inside the storage facility. Six hours is the commonly used minimum contact time for this procedure, ensuring a reliable disinfection under typical conditions and allowing the chlorine to mix evenly throughout the tank.

Two hours is usually not enough for thorough disinfection, while twelve or twenty-four hours are longer than necessary for this method and can complicate operations. After the six-hour contact period, you’d verify the chlorine residual meets the target before proceeding to fill with potable water.