Exam CFPS Topic 7 Question 138 Discussion

Explanation
valve at the inspector's test connection.
For wet-pipe automatic sprinkler systems, the only proper way to test the operation of a vane-type water flow alarm initiating device is to open the valve at the inspector's test connection. This is a small valve that is located at the end of a pipe that is connected to the sprinkler system, usually at the most remote or highest point. The inspector's test connection simulates the flow of a single sprinkler head and activates the vane-type water flow switch, which in turn triggers the fire alarm panel and the external alarm devices.Opening the valve at the inspector's test connection also allows the water to drain from the system, preventing corrosion and freezing1234 Opening the main (2 in. diameter) drain is not a proper way to test the operation of a vane-type water flow alarm initiating device, because it does not create enough flow to activate the switch. The main drain is used to drain the entire sprinkler system for maintenance or repair purposes, and it is usually located at the main riser or the fire department connection.Opening the main drain may also cause a pressure drop in the system, which could affect the performance of the sprinklers1234 Opening the alarm test by-pass valve at the system's main riser is not a proper way to test the operation of a vane-type water flow alarm initiating device, because it does not simulate the actual flow of a sprinkler head.
The alarm test by-pass valve is used to test the operation of the external alarm devices, such as the water motor gong or the electric bell, without activating the fire alarm panel. The alarm test by-pass valve is usually located near the alarm check valve or the water flow switch, and it allows water to flow through a small orifice to the alarm devices.Opening the alarm test by-pass valve does not create enough flow to activate the vane-type water flow switch1234 Opening the check valve from the city connection is not a proper way to test the operation of a vane-type water flow alarm initiating device, because it does not create any flow in the sprinkler system. The check valve from the city connection is used to prevent the backflow of water from the sprinkler system to the city water supply, and it is usually located at the fire department connection or the main riser.Opening the check valve from the city connection does not affect the water flow in the sprinkler system, and it does not activate the vane-type water flow switch1234 References:
Fire Sprinkler Flow Switch & Tamper Switch Inspection & Maintenance3
Sprinkler System Water Flow Device Testing - ORR Protection2
VSR-AT Auto-Test Waterflow Alarm Switch | Potter Electric4
WFDNA Series Vane-type Waterflow Detectors - Steel Fire Equipment5