During pipe disinfection, the chlorine solution is usually injected through a ______ at the point where the new main connects to the existing system.

• A. Corporation Stop
• B. Gate Valve
• C. Hydrant
• D. Tapping Tee

Answer: (A)

When disinfecting a new main, you want a controlled, accessible point to introduce the chlorine into the flow as the tie-in to the existing system is made. A corporation stop provides a secure port on the service line off the existing main, allowing chlorine solution to be injected directly into the pressurized water at the connection point. This placement ensures the disinfectant reaches the interior surfaces of the new pipe as it becomes part of the distribution system. Using a gate valve is mainly for stopping and starting flow, not for injecting disinfectant through the valve mechanism; a hydrant is suited for flushing or sampling rather than introducing chlorine into the main; and a tapping tee is a construction fitting used to create the tie-in itself, not the site where chlorine is injected during the disinfection process.