What kind of valve allows flow in only one direction?

A check valve is specifically designed to allow fluid to flow in only one direction, preventing backflow in a piping system. This is crucial in various applications, such as water and sewage systems, to ensure that liquids do not flow backwards and cause contamination or system failure. The operation of a check valve involves a movable component, often a disc or ball, that opens when flow is in the desired direction and closes when flow attempts to reverse. This mechanism ensures that the flow direction is maintained, protecting the integrity of the system.

In contrast, a needle valve is typically used for precise flow control, not directional flow management. A gate valve is used to fully open or close a flow path, and it does not provide any control over backflow. A globe valve is primarily used to regulate flow and is not designed for preventing backflow either. Therefore, the check valve stands out as the correct answer due to its unique function of ensuring one-directional flow in piping systems.