Published on November 28, 2025
Your fire pump system relies on pressure switches and gauges to monitor system health and trigger automatic operation. These components are the "eyes" of your system—they watch pressure continuously and ensure your pump responds correctly when needed. Yet when pressure switches fail or gauges become inaccurate, your entire fire protection system can malfunction.
At Apex Pumps, we've seen countless systems fail because of faulty pressure switches or inaccurate gauges that went undetected until an emergency. Understanding how these components work, recognizing signs of failure, and knowing when to replace or calibrate them is essential for maintaining system reliability and AS1851 compliance.
This comprehensive guide covers everything you need to know about fire pump pressure switches and gauges—from how they work to failure signs, calibration vs replacement decisions, pressure range selection, and AS1851 testing requirements.
What Are Pressure Switches and Gauges?
Pressure switches and gauges are critical monitoring components in your fire pump system. While they serve different functions, both are essential for system operation and compliance.
Pressure Switches
A pressure switch is an automatic control device that monitors system pressure and triggers the fire pump to start when pressure drops below a set point (cut-in pressure) and stops the pump when pressure is restored (cut-out pressure). It's the component that makes your fire pump system automatic—without it, the pump would need manual operation.
Key functions of pressure switches:
- Automatic Pump Control: Starts pump when pressure drops, stops when pressure is restored
- Pressure Monitoring: Continuously monitors system pressure via a sensing element
- Set Point Control: Adjustable cut-in and cut-out pressures for system optimization
- Safety Function: Prevents pump from running when not needed, protecting system components
Pressure Gauges
Pressure gauges provide visual indication of system pressure in real-time. They allow operators and technicians to see current system pressure, verify pump operation, and diagnose system issues. Oil-filled gauges are preferred for fire pump applications because they reduce vibration and provide more stable readings.
Key functions of pressure gauges:
- Visual Monitoring: Real-time pressure indication for operators and technicians
- Diagnostic Tool: Helps identify pressure problems and system issues
- Verification: Confirms pressure switch operation and pump performance
- Compliance Documentation: Provides visual evidence of system pressure during testing
How Pressure Switches Work
Understanding how pressure switches function helps you recognize problems and make informed decisions about replacement or calibration.
Pressure switches use a sensing element (typically a diaphragm or bellows) that responds to system pressure. When pressure drops below the cut-in setting, the switch closes an electrical circuit, sending a signal to the control panel to start the pump. When pressure rises to the cut-out setting, the switch opens the circuit, signaling the pump to stop.
Common pressure switch types available from Apex Pumps:
- Telemanique XMP: Available in 12 bar and 25 bar ranges, known for reliability and accuracy
- MDR Condor: 800-2500kPa range with on/off switching capability
- Danfoss Style: Available in 16 bar and 20 bar configurations
- Potter PS120-1: Reliable option for various pressure ranges
The correct pressure switch depends on your system's working pressure. Using a switch with too low a range can cause premature wear, while one with too high a range may not respond correctly to pressure changes. Apex Pumps can assess your system and recommend the appropriate pressure switch.
Understanding Pressure Gauges: Oil-Filled vs Standard
Pressure gauges come in two main types: standard (dry) and oil-filled. For fire pump applications, oil-filled gauges are strongly recommended.
Oil-Filled Gauges
Oil-filled gauges contain a damping fluid (usually glycerin or silicone) that fills the gauge case. This fluid provides several advantages:
- Vibration Damping: Reduces pointer oscillation and vibration damage
- Extended Life: Protects internal mechanisms from wear caused by vibration
- Stable Readings: Provides smoother, more readable pressure indication
- Lubrication: Keeps internal components lubricated and functioning smoothly
- Corrosion Protection: Helps protect internal components from moisture and corrosion
Apex Pumps stocks oil-filled gauges in various sizes and pressure ranges:
- 63mm Gauges: Available in 0-1600kPa and 0-2500kPa ranges, with 1/4" bottom or rear entry
- 100mm Gauges: Available in 0-1600kPa and 0-2500kPa ranges, with 3/8" bottom entry
Standard (Dry) Gauges
Standard gauges don't contain damping fluid. While they're simpler and less expensive, they're more prone to:
- Pointer oscillation and vibration damage
- Shorter lifespan in high-vibration environments
- Less stable readings
- Higher maintenance requirements
For fire pump applications where vibration is common, oil-filled gauges are the better choice for reliability and longevity.
Choosing the Right Pressure Range
Selecting the correct pressure range for switches and gauges is critical for accurate monitoring and reliable operation. The range must match your system's working pressure while providing adequate monitoring capability.
Factors to consider when choosing pressure ranges:
- System Working Pressure: The gauge/switch range should be 1.5-2 times your normal working pressure
- Maximum System Pressure: Must accommodate peak pressures during pump operation
- Accuracy Requirements: Larger ranges provide less accuracy; choose the smallest range that covers your needs
- AS1851 Requirements: Must meet minimum accuracy and range requirements for compliance
Common pressure ranges available from Apex Pumps:
- 12 bar (1200kPa): For lower pressure systems
- 16 bar (1600kPa): Common for standard fire pump applications
- 20 bar (2000kPa): For higher pressure systems
- 25 bar (2500kPa): For high-pressure applications
- 0-1600kPa: Standard range for many fire pump systems
- 0-2500kPa: Extended range for high-pressure applications
If you're unsure about the correct pressure range, our technicians can assess your system during routine maintenance and recommend the appropriate range. Using the wrong range can lead to inaccurate readings, premature failure, or non-compliance.
Signs Your Pressure Switch or Gauge Needs Attention
Recognizing early warning signs can prevent system failure and ensure compliance. Watch for these indicators:
Pressure Switch Warning Signs:
- Pump Won't Start: Switch fails to trigger pump when pressure drops
- Pump Won't Stop: Switch fails to stop pump when pressure is restored
- Erratic Operation: Pump cycles too frequently or irregularly
- Incorrect Set Points: Switch activates at wrong pressures despite adjustment
- Physical Damage: Corrosion, leaks, or damaged sensing elements
- Failed Calibration: Cannot be calibrated to required accuracy
Pressure Gauge Warning Signs:
- Inaccurate Readings: Gauge shows incorrect pressure compared to known standards
- Pointer Sticking: Pointer doesn't move or sticks at certain pressures
- Excessive Vibration: Pointer oscillates excessively (may indicate need for oil-filled gauge)
- Broken Glass: Damaged gauge face or broken glass
- Leaking: Oil-filled gauge leaking damping fluid
- Zero Error: Gauge doesn't return to zero when pressure is released
If you notice any of these signs, schedule immediate inspection and testing. Early detection prevents system failure and ensures AS1851 compliance.
When to Replace vs Calibrate
Deciding whether to replace or calibrate a pressure switch or gauge depends on several factors. Understanding the difference helps you make cost-effective decisions while maintaining system reliability.
When Calibration Is Appropriate
Calibration is suitable when the device is still functional but showing slight inaccuracies:
- Device is relatively new (less than 3-5 years old)
- Inaccuracy is minor and within calibration range
- No physical damage or component failure
- Calibration can restore accuracy to within AS1851 requirements
- Device has been functioning well with only minor drift
When Replacement Is Necessary
Replacement is required when calibration isn't possible or cost-effective:
- Device fails calibration or cannot be calibrated to required accuracy
- Physical damage (corrosion, leaks, broken components)
- Device is old (typically 5-10 years for switches, longer for gauges)
- Repeated calibration failures or excessive drift
- Incompatible with system upgrades or requirements
- Replacement parts are no longer available
- Cost of calibration exceeds replacement cost
During routine testing, our technicians assess each device and provide recommendations for calibration or replacement based on condition, accuracy, and cost-effectiveness.
AS1851 Compliance and Testing Requirements
Pressure switches and gauges are critical components under AS1851 and must be regularly tested and calibrated. The testing schedule includes:
- Monthly: Visual inspection
- Six-monthly: Operation and accuracy checks
- Annually: Calibration verification
- Five-yearly: Comprehensive service
During routine testing, our technicians use calibrated test equipment to verify pressure switch operation and gauge accuracy. All testing is documented, and recommendations are provided for calibration or replacement if devices fall outside acceptable tolerances.
Why Choose Apex Pumps for Pressure Switch and Gauge Services?
When it comes to pressure switches and gauges, Apex Pumps offers comprehensive solutions:
- Complete Stock: We stock pressure switches from leading brands (Telemanique, MDR Condor, Danfoss, Potter) in various pressure ranges
- Oil-Filled Gauges: Comprehensive range of oil-filled gauges in 63mm and 100mm sizes with various pressure ranges
- Expert Assessment: Our technicians can assess your system and recommend the correct pressure range and device type
- Calibration Services: Professional calibration services using calibrated test equipment
- AS1851 Compliance: All testing and replacement work performed according to Australian standards
- Quick Service: Fast turnaround for replacement to minimize system downtime
Don't let faulty pressure switches or inaccurate gauges compromise your fire protection system. Contact Apex Pumps for assessment, testing, calibration, and replacement services that keep your system compliant and reliable.
Final Thoughts: Don't Overlook the Monitoring Components
Pressure switches and gauges may seem like small components, but they're the eyes that monitor your entire fire protection system. When they fail, your system can't respond correctly to emergencies, putting lives and property at risk.
Understanding how these components work, recognizing failure signs, and ensuring proper maintenance and testing are essential for compliance, safety, and peace of mind. Whether you need pressure switch replacement, gauge calibration, or routine testing, Apex Pumps has the expertise and stock to keep your system operational.
If your pressure switches or gauges are showing signs of failure, haven't been tested recently, or are more than 5 years old, don't wait. Contact the Apex Pumps team today for an assessment and ensure your fire protection system's monitoring components are ready when seconds count.