What is the required valve position to begin a main drain test?

To properly conduct a main drain test, the alarm control valve must be closed, while the main drain valve should be open. This configuration allows for the flow of water from the system through the main drain, enabling an accurate assessment of the system's pressure and flow characteristics.

Opening the main drain allows water to exit the system, which helps evaluate the performance of the system and its components under conditions that simulate a fire event. Conversely, having the alarm control valve closed prevents water from flowing to the alarm system, ensuring that the test conditions reflect a scenario where the system is not actively providing water to the fire protection devices, thus simulating the draining of water from the system realistically.

This setup aligns with NFPA standards and requirements for testing to ensure the effectiveness and reliability of fire protection systems. Correctly positioning the valves is essential for achieving valid test results and maintaining compliance with safety regulations.