On a check valve, what indicates the direction of fluid flow?

In plumbing systems, a check valve is designed to allow fluid to flow in only one direction, preventing backflow. The direction of fluid flow is indicated by an arrow that is typically marked on the valve body. This arrow is crucial for installation, as it guides plumbers on how to orient the valve correctly within the piping system to ensure it functions as intended.

The arrow serves a practical purpose by clearly showing the intended flow path, thus making it easier to install the valve properly. When the valve is positioned with the arrow pointing in the direction of fluid flow, it ensures that the check mechanism operates effectively, preventing any unwanted reverse flow.

While other methods, such as labels or symbols, can provide additional information about a valve, the arrow specifically communicates the correct directional flow, which is essential for the proper operation of the check valve. Understanding this visual cue is vital for anyone involved in plumbing to ensure system safety and efficiency.