Which of the following is a common automatic start condition for a fire pump?

• A. Time of day
• B. Activation of a smoke detector
• C. A rise in discharge pressure
• D. A drop in system pressure below a preset threshold

Answer: (D)

Automatic start of a fire pump is driven by system demand reflected in pressure loss. When the system pressure falls below a preset value, a pressure-sensing device signals the pump controller to start the pump, bringing the pressure back up to the required level and ensuring adequate flow to the protected areas. This method directly responds to actual need rather than a schedule or unrelated events, which is why it’s the standard automatic-start mechanism. A rise in discharge pressure would indicate the system is already pressurized or the pump is already delivering, so it would not initiate starting. Time of day isn’t tied to immediate system demand, and while detectors can trigger alarms or other actions in some configurations, they’re not the common automatic start signal for the fire pump.