What is the name of the valve designed for connecting a new water main to an existing main that is under pressure?

The valve specifically designed for connecting a new water main to an existing main that is under pressure is known as a tapping valve. This type of valve allows for the installation of a branch line from the existing main without interrupting service or depressurizing the system. Tapping valves are constructed to handle the pressure from the water in the existing main and ensure a secure connection.

A check valve primarily prevents backflow in a pipeline, while a ball valve is used to start or stop the flow of water but is not specifically designed for installations under pressure. A gate valve, commonly used for isolation purposes, is not ideal for this application as it is meant for fully open or closed conditions rather than for connecting lines under pressure. Tapping valves are critical in maintaining the integrity and continuous operation of the water distribution system while facilitating necessary expansions or modifications.