Which dichlorination method has the disadvantages of possible overdosing, under dosing, and being hard to tell when the chemical has been depleted?

• A. flow-through systems
• B. batch dosing
• C. premixed solution
• D. point dosing

Answer: (A)

Flow-through dosing adds the chlorine continuously as water moves through the system, so the amount delivered is tied to the real-time flow rate and contact time. Because flow and demand can vary, the actual residual in the water can drift—leading to periods of overdosing when flow drops or demand is lower, and underdosing when flow increases or demand rises. Since the chemical is not stored as a defined dose and its presence is spread along the pipe, it’s hard to tell exactly when it has been depleted, making it difficult to know when to add more. This combination of variable delivery and hidden depletion is why overdosing, under dosing, and undetected depletion are common with this method.