A jockey pump is a small pump that keeps fire sprinkler pipes pressurized at all times, so the system is ready to respond the instant a sprinkler head opens. It’s not the pump that fights a fire. Its job is to compensate for tiny, normal pressure drops in the piping and prevent the main fire pump from starting unnecessarily.
How a Jockey Pump Works
Fire sprinkler systems need to stay at a specific pressure so that when a sprinkler head activates during a fire, the sudden pressure drop is large enough for the fire pump controller to detect and trigger the main pump. Without a jockey pump, small leaks, temperature changes, or normal seepage in the piping would slowly lower the system pressure. That gradual decline could eventually trick the controller into starting the main fire pump even though there’s no fire.
The jockey pump prevents this by cycling on automatically when pressure dips slightly, topping the system back up before the pressure falls low enough to trigger the main pump. Think of it like a car’s tire pressure monitor paired with a tiny air compressor that kicks on whenever a tire loses a pound or two of air. The jockey pump keeps the system “charged” and ready without waking up the much larger, more powerful fire pump.
Pressure Settings and Thresholds
The jockey pump and main fire pump operate at different pressure thresholds, and the gap between them is what makes the system work. The jockey pump’s shutoff pressure is set at least 10 psi above the main fire pump’s churn pressure (the pressure the fire pump produces when running but not flowing water). So if the main fire pump’s churn pressure is 130 psi, the jockey pump would be set to maintain around 140 psi in the system.
The jockey pump itself has a start and stop point separated by about 10 psi. When system pressure drops to the start point, the jockey pump kicks on and runs until it reaches the stop point, then shuts off. As long as the pressure loss is just normal seepage, the jockey pump handles it. But if a sprinkler head opens during a fire, the pressure drop is far too rapid and large for the little jockey pump to compensate for. Pressure falls past the jockey pump’s range and hits the main fire pump’s activation threshold, which is exactly what should happen.
Sizing: Intentionally Small
A jockey pump is deliberately sized to move less water than a single sprinkler head would flow. This is a key design feature, not a limitation. If the jockey pump could keep up with even one open sprinkler, the main fire pump might never start during a real fire.
For systems with only above-ground piping (sprinkler lines and standpipes inside a building), the pump just needs to offset minor pressure fluctuations. For systems that also serve underground water mains, sizing follows a common rule of thumb: 1% of the main fire pump’s rated capacity. A building with a 1,500-gallon-per-minute fire pump would have a jockey pump rated at about 15 gallons per minute. Another guideline used for underground mains is selecting a pump that can make up the allowable leakage rate in 10 minutes, or 1 gallon per minute, whichever is larger.
Where Jockey Pumps Are Installed
You’ll find jockey pumps in virtually any building with an automatic fire sprinkler system and an electric or diesel fire pump. Commercial buildings, high-rises, warehouses, hospitals, schools, and industrial facilities all use them. The jockey pump sits near the main fire pump in the fire pump room, connected to the same sprinkler piping but with its own controller and its own electrical supply. Fire protection codes specifically require that the jockey pump’s electrical wiring not be connected through the fire pump controller, keeping the two systems independent.
Unlike the main fire pump, a jockey pump doesn’t need a backup power source. It’s a maintenance device, not an emergency device. If the building loses power and the jockey pump stops running, the main fire pump (which does require a reliable or alternate power supply) can still activate when needed.
Common Problems: Frequent Cycling
The most common issue with jockey pumps is rapid cycling, sometimes called “chattering.” This is when the pump starts and stops repeatedly in quick succession instead of running briefly and staying off for a reasonable period. Rapid cycling wears out the pump motor, stresses seals, and can indicate a deeper problem in the sprinkler system.
The usual culprit is a leak somewhere in the piping. If water is escaping faster than normal seepage, the jockey pump runs to restore pressure, shuts off, then immediately detects another pressure drop and starts again. A leaking check valve, a damaged fitting, or deteriorating underground pipe joints can all cause this pattern. In high-rise buildings, pressure-reducing valves on individual floors sometimes develop small leaks that equalize pressure across zones, creating persistent instability the jockey pump can’t overcome.
If you notice a jockey pump cycling every few minutes (or more frequently), it’s a sign that something in the system needs inspection. The pump itself may be fine, but the condition it’s reacting to needs to be found and fixed.
Weekly Inspection Basics
Jockey pumps require simple, routine checks. Standard fire pump inspection checklists include verifying that the jockey pump has power (the controller pilot light should be illuminated), that suction and discharge valves are open, and that system pressure readings are within the normal range. These checks take minutes but confirm the pump is ready to do its job: quietly maintaining pressure so the main fire pump only runs when there’s an actual fire.