What type of tee and valve combination is used to install on a water main without shutting it down?

The appropriate combination for installing on a water main without shutting it down involves using a specific method designed for such purposes. Tapping tees and tapping valves are specifically engineered to allow for connections to be made on pressurized water mains. This is crucial for maintaining service continuity without interrupting the flow of water in the system.

Tapping tees facilitate the installation process by allowing a small opening to be made in the main, which can then be connected to the new service line using a tapping valve. The tapping valve serves to control the flow of the water during the process of installing the new connection. This method is preferred in many municipal systems when it is necessary to expand or repair the water distribution network without service interruption.

Other combinations, such as wye tees with ball valves or standard tees with gate valves, typically require more significant modifications and system shutdowns, which is not ideal for emergency situations or in systems that need to maintain constant supply. Likewise, service tees and check valves are not specifically designed for hot tap applications where main line connections are needed without interruption.