What is the minimum working pressure required for the system?

What is the minimum working pressure required for the system?

• A. 150 psi
• B. 175 psi
• C. 200 psi
• D. 125 psi

Answer: (B)

The minimum working pressure is the lowest pressure the system must be able to maintain during normal operation to ensure all sprinklers receive adequate flow, even with friction losses and elevation differences in the network. For NFPA 13R low-rise residential designs, the standard practice sets this operating minimum at 175 psi. This ensures there’s enough pressure to meet the design flow to all sprinklers while staying within typical component ratings and pump capabilities. The hydrostatic test uses a higher pressure (200 psi) to verify the piping can withstand that load, but that isn’t the operating pressure. The other values would not provide the required operating headroom for reliable sprinkler performance under design conditions.

The minimum working pressure is the lowest pressure the system must be able to maintain during normal operation to ensure all sprinklers receive adequate flow, even with friction losses and elevation differences in the network. For NFPA 13R low-rise residential designs, the standard practice sets this operating minimum at 175 psi. This ensures there’s enough pressure to meet the design flow to all sprinklers while staying within typical component ratings and pump capabilities. The hydrostatic test uses a higher pressure (200 psi) to verify the piping can withstand that load, but that isn’t the operating pressure. The other values would not provide the required operating headroom for reliable sprinkler performance under design conditions.