Which device is essential for controlling water flow from the pipe system?

The device that is essential for controlling water flow from the pipe system is a valve. Valves are critical components in plumbing systems that allow for the regulation, control, or direction of fluid flow. They can be used to start or stop the flow, adjust the flow rate, and manage the direction of the water through the plumbing system.

Faucets, while they do control the flow of water at a specific point, are typically designed for user operation in delivering water for various tasks (e.g., washing hands, dishes). However, they function as a type of valve, but they are not universally applicable throughout the entire plumbing system.

Tanks and drains serve different purposes; a tank stores water while a drain is designed to remove water from a system. Therefore, while tanks and drains are important to the function of a plumbing system, they do not directly control the flow of water within the pipes. Valves are universally essential in all types of plumbing configurations to manage water flow effectively.