The relief valve on your air compressor serves as a critical safety device, designed to open and release excess pressure when the internal tank pressure exceeds a safe limit. If it keeps popping, it indicates a problem that needs immediate attention, as it can be either a sign that excessive pressure is building up inside the compressor or a sign of the valve itself failing.
Understanding the root cause is crucial for both safety and proper compressor operation.
Common Causes of Excessive Pressure Build-up
When the relief valve activates due to overpressure, it means the compressor's primary pressure regulation systems are failing, leading to dangerous conditions.
1. Malfunctioning Pressure Switch
The pressure switch is the brain of your compressor, responsible for telling the motor to start when pressure drops and to stop when the desired maximum pressure is reached.
- Problem: If the pressure switch fails to shut off the compressor motor at its set cut-out pressure, the compressor will continue to run, building pressure beyond its safe limit until the relief valve pops.
- Troubleshooting & Solution:
- Listen: Does the compressor continue to run even after the tank gauge shows it has reached its maximum pressure setting?
- Inspect: Check the pressure switch wiring and connections.
- Test: With the compressor running, observe the pressure gauge. If it goes past the cut-out pressure and doesn't stop, the switch is likely faulty.
- Action: A faulty pressure switch typically needs to be replaced.
2. Stuck Unloader Valve or Check Valve
These two valves work in conjunction to manage airflow and pressure.
- Unloader Valve: Releases air from the compressor pump when the motor stops, allowing for an easier restart against no pressure. If it sticks closed, the pump tries to start under load, which can sometimes lead to motor issues or, indirectly, pressure buildup if it interferes with the pressure switch's operation.
- Check Valve: Located between the compressor pump and the air tank, it prevents compressed air from flowing back into the pump when the motor stops. If it sticks open, tank air can leak back into the pump, putting a constant load on the motor, and potentially causing the compressor to run continuously and build excessive pressure.
- Troubleshooting & Solution:
- Listen: After the compressor shuts off, do you hear a hiss of air quickly escaping from the unloader valve? If not, it might be stuck closed.
- Observe: If the compressor labors to restart or the motor hums without turning the pump, it could indicate a stuck check valve allowing tank pressure back to the pump.
- Action: Inspect and clean the unloader valve or check valve. If they are heavily corroded or damaged, replacement is necessary.
3. Clogged Air Filter
While less direct, a severely clogged air filter can sometimes contribute to a compressor overworking, potentially leading to issues with other components that regulate pressure.
- Problem: Restricts airflow into the compressor, making the pump work harder and less efficiently. This can cause increased heat and strain on components, potentially affecting pressure sensor accuracy or valve operation over time.
- Troubleshooting & Solution:
- Inspect: Visually check the air filter. Is it dirty, dusty, or crumbling?
- Action: Replace the air filter regularly according to your compressor's maintenance schedule.
4. Blocked Discharge Line or Regulator Issues
Obstructions in the air lines or a faulty pressure regulator can cause pressure to build up upstream of the obstruction or within the tank itself if the regulator is not allowing proper air output.
- Problem: If the main discharge line from the tank is blocked or the primary pressure regulator is set incorrectly or failing to release air effectively, the pressure in the tank can quickly rise.
- Troubleshooting & Solution:
- Check: Ensure all valves on the tank outlet are open and no lines are kinked or blocked.
- Verify Regulator: If your compressor has an adjustable regulator, ensure it's set correctly. If it's malfunctioning, it might not be passing air efficiently, leading to tank overpressure.
- Action: Clear any obstructions. Adjust or replace the pressure regulator if it's faulty.
Issues with the Relief Valve Itself
Sometimes, the problem isn't excessive pressure but the relief valve malfunctioning prematurely or incorrectly.
1. Defective or Worn Relief Valve
Even a safety device can fail over time due to wear, fatigue, or manufacturing defects.
- Problem: The spring inside the valve can weaken, or the seal can degrade, causing it to open at pressures below its rated set point. This means it pops even when the tank pressure is within normal operating limits.
- Troubleshooting & Solution:
- Observe: Does the valve pop when the pressure gauge shows a normal operating pressure (e.g., 90-100 PSI) well below its stated release pressure (e.g., 150 PSI)?
- Test (Carefully): A quick tug on the ring of the relief valve can confirm it's not stuck, but if it pops too easily or frequently at low pressures, it's likely faulty.
- Action: A relief valve that opens at the wrong pressure cannot be repaired and must be replaced with one specifically rated for your compressor's maximum safe working pressure.
2. Incorrectly Rated or Set Relief Valve
- Problem: If a replacement valve with an incorrect pressure rating was installed, or if the original valve was simply wrong for the compressor's design (unlikely for factory new, but possible with used or repaired units), it will pop prematurely or not at all (which is even more dangerous).
- Troubleshooting & Solution:
- Check Label: Inspect the relief valve for its pressure rating (e.g., "150 PSI"). Compare this to your compressor's maximum tank pressure rating (usually found on a data plate or in the owner's manual). The relief valve rating should be at or slightly above your compressor's maximum operating pressure but below the tank's absolute maximum safe working pressure.
- Action: Replace with the correct relief valve for your specific compressor model.
3. Contamination or Debris
- Problem: Dirt, rust, or other debris can get lodged in the valve's seating mechanism, preventing it from sealing properly or causing it to stick partially open or pop erratically.
- Troubleshooting & Solution:
- Action: Lightly pull the ring on the relief valve to cycle it a few times (with caution and eye protection). This can sometimes clear minor debris. If the problem persists, the valve needs to be replaced.
What to Do When Your Relief Valve Keeps Popping
- Stop Operation Immediately: If the relief valve is frequently popping, turn off the compressor and disconnect it from power.
- Identify the Cause: Systematically go through the potential issues listed above.
- Inspect and Diagnose:
- Check the pressure switch for proper operation.
- Examine the unloader and check valves.
- Inspect the air filter.
- Ensure discharge lines are clear.
- Verify the relief valve's rating and condition.
- Replace Faulty Components: Do not attempt to repair safety components like the relief valve. Replace them with parts specifically designed for your compressor model and pressure requirements. Always consult your compressor's owner's manual for specific troubleshooting steps and replacement part numbers. If unsure, consult a qualified technician.
Safety Note: Never attempt to disable or tamper with the relief valve. It is a critical safety device designed to prevent catastrophic tank rupture, which can cause severe injury or death.
