Fire pumps are the beating heart of many fire protection systems, ensuring water is delivered at the right pressure to sprinklers, standpipes, and hydrants when it’s needed most. But what actually tells a fire pump to start? The activation process is not random—it’s a carefully designed sequence driven by sensors, controls, and safety codes.
In this guide, we’ll explore the triggers that activate a fire pump, the difference between automatic and manual start, and how NFPA 20 requirements shape pump activation. Whether you’re a facility manager, fire protection contractor, or safety engineer, understanding how a fire pump is activated is essential for keeping systems reliable and compliant.
Before looking at activation, it’s important to understand why a fire pump exists. In simple terms, a fire pump boosts water pressure so the system can deliver enough water flow to suppress a fire.
Fire pumps are commonly installed when:
The water supply (municipal or tank) doesn’t provide adequate pressure.
High-rise buildings require pressure to reach upper floors.
Systems like deluge or foam suppression need higher flow rates.
Because fire pumps are mission-critical, their activation must be immediate, reliable, and fail-safe. That’s why fire pump controllers, sensors, and backup systems work together to detect demand and start the pump instantly.
The most common trigger for a fire pump is a drop in system pressure. This is typically detected by a pressure sensing device, often a pressure switch or pressure transducer, installed in the piping between the pump discharge and the system’s check valve.
Under normal conditions, the pump is off and system pressure remains stable.
When a sprinkler head opens or a hose valve is used, water flows out of the system.
This flow causes a drop in pressure in the fire protection piping.
The pressure sensing device detects the drop and signals the fire pump controller to start the pump.
According to NFPA 20 (Standard for the Installation of Stationary Pumps for Fire Protection), the pump should start automatically when pressure drops to a pre-set level—commonly 10 psi (0.7 bar) below normal.
The fire pump controller is essentially the “brain” that receives signals from sensors and commands the pump to start or stop. It can initiate pump operation in several ways:
Automatic start: From pressure drop detection.
Manual start: Via start button on the controller.
Remote manual start: From a fire command center or remote panel.
Controllers also handle safety features such as:
Sequential starting of multiple pumps.
Automatic transfer to backup power.
Alarm and status indication.
Automatic start is the preferred and most common method. In an emergency, it ensures the pump starts without human intervention, which is crucial if the fire occurs in an unoccupied area or at night.
NFPA 20 also requires that fire pumps can be started manually. Manual start methods include:
Local start button on the controller.
Remote start station.
Fire alarm system integration.
Manual start is often used during testing, maintenance, or as a backup if automatic start fails.
While pressure drop is the main trigger, there are other ways a fire pump can be activated:
Flow Switch in Sprinkler Systems – Detects actual water movement.
Fire Alarm System Signal – Certain systems integrate pump activation with alarm triggers.
Building Automation System (BAS) – For facilities with centralized monitoring.
In specialized applications, such as foam systems or deluge systems, pump activation can be triggered by solenoid valves opening, releasing water or foam concentrate into the piping.
Electric-driven pumps start almost instantly when the controller energizes the motor. They rely on a stable power source, which is why emergency generators are often provided.
Diesel pumps require a slightly longer start time since the engine must crank before running. They use batteries and starter motors controlled by the fire pump controller, and NFPA 20 requires them to start within 10 seconds of a start signal.
Because fire protection cannot fail, most systems use redundant sensing devices. NFPA 20 requires:
Two pressure sensing lines (one for each sensing device).
Independent circuits for manual and automatic start.
This redundancy ensures that if one device fails, the other can still activate the pump.
Even the best-designed system can fail if not properly maintained. Common problems include:
Pressure switch malfunction – Incorrect calibration or failure to detect drops.
Controller faults – Electrical or software issues preventing start signals.
Blocked sensing lines – Dirt or corrosion preventing accurate readings.
Battery failure (for diesel pumps) – Insufficient cranking power.
Routine inspection and testing—monthly no-flow tests and annual full-flow tests—are vital to ensure activation works as intended.
NFPA 25 (Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems) outlines procedures to verify pump activation.
Monthly (No-Flow Test):
Start the pump automatically via pressure drop.
Confirm proper start time.
Check controller response and alarm signals.
Annual (Flow Test):
Open test header to simulate actual demand.
Verify pressure drop starts the pump.
Measure pump performance against nameplate data.
Knowing what activates a fire pump is more than technical trivia—it’s essential for:
System Design – Ensuring triggers are reliable and compliant.
Maintenance Planning – Identifying potential failure points.
Emergency Preparedness – Training staff to recognize and manually start pumps if needed.
When lives and property are at stake, a fire pump’s activation sequence must be immediate, reliable, and well-maintained.
A fire pump is activated primarily by a pressure drop in the fire protection piping, detected by a pressure switch or transducer, and relayed to a fire pump controller. This automatic start is backed up by manual controls, redundancy, and compliance with NFPA 20 requirements.
Whether powered by an electric motor or a diesel engine, the key is ensuring the activation sequence is fail-proof. Through proper design, regular testing, and maintenance, you can guarantee your fire pump will respond exactly when it’s needed—without delay.
