What type of valve prevents backflow, allowing flow in one direction?

A check valve is specifically designed to permit fluid flow in only one direction, effectively preventing backflow. This function is essential in various plumbing and fluid systems to prevent contamination and keep processes functioning correctly.

Check valves work automatically, typically utilizing a disc or ball mechanism that opens with forward flow and closes when the flow reverses, thereby blocking reverse flow. This characteristic is crucial in applications such as sewage systems, irrigation, and any system requiring a safeguard against backflow that could lead to contamination or system failure.

The other types of valves listed do not serve the same purpose as a check valve. A gate valve is used primarily for on/off control, providing a clear passage when open but not designed to prevent backflow. A ball valve is also used for on/off control and provides a tight seal when closed, but it does not inherently prevent backflow the way a check valve does. A pressure relief valve is designed to release excess pressure from a system to prevent damage, rather than to control the direction of flow.