Every sprinkler system should be equipped with a main control valve located between the:

• A. riser and the branches
• B. source of water supply and the sprinkler system
• C. cross mains and the riser
• D. fire department connection and the riser

Answer: (B)

The main control valve serves as the primary shut-off for the entire sprinkler system, so it must be placed at the boundary where the building’s water supply enters the sprinkler system. This location allows you to completely stop water flow into the system for maintenance, testing, or emergencies, affecting all sprinkler lines at once rather than just a portion of the network. If the valve were placed downstream of the riser, cross mains, or after any branches, water could still reach parts of the system, defeating the purpose of a full isolation. Similarly, placing it after the fire department connection wouldn’t provide a true shut-off of the system from the main supply. Therefore, the correct placement is between the water source and the sprinkler system.