What indicates a failure in a check valve during testing?

A failure in a check valve during testing is indicated by pressure loss. When a check valve is functioning properly, it prevents backflow within a system, maintaining a consistent pressure on the supply side. If there is a pressure loss during testing, it suggests that the valve is not sealing correctly, allowing fluid to flow back in the opposite direction, which compromises the system's integrity and can lead to contamination or other operational issues.

On the other hand, zero pressure reading would indicate a complete loss of system pressure, which could be caused by factors unrelated to the check valve itself. A high flow reading suggests that there is a significant flow rate through the system, which does not inherently indicate a check valve failure but may suggest other issues, such as excess demand or a malfunction in another component. Static pressure gain would imply that pressure is being built up in the system, which also does not reflect the condition of the check valve, as this may occur under various conditions without indicating backflow or a failure of the valve's function.