Which equipment is used to conduct a water flow test on a sprinkler system?

The inspector test valve is the correct choice for conducting a water flow test on a sprinkler system. This valve is specifically designed to allow for testing the operation and performance of the sprinkler system by simulating what would happen during a fire. It provides a way to release water from the system, which helps to measure flow rates, pressure, and the overall effectiveness of the system.

During a water flow test, using the inspector test valve allows for a controlled environment to assess how well the sprinkler system performs under flow conditions that mimic a fire event. This information is critical for ensuring that the system is functioning properly and meets fire safety codes and standards.

The other equipment mentioned has different purposes. A flow meter measures the rate of water flow but is not the primary mechanism used to initiate a water flow test. A pressure gauge provides information about the water pressure in the system but does not directly facilitate the flow test itself. The control valve regulates the water supply to the sprinkler system but is not utilized for testing the flow in the same way an inspector test valve is. Thus, the focus on the testing capability of the inspector test valve makes it the ideal choice for this situation.