What does the Vaillant F75 Fault code mean?
The Vaillant F75 fault code is a common issue found on Vaillant ecoTEC boilers and is usually linked to a problem with water pressure detection during boiler start-up.
This article explains what the Vaillant F75 fault code means, the most common causes, and what can be done to resolve it safely.
Vaillant boilers are widely used across the UK due to their reliability, but like all heating systems, faults can occur. When they do, your boiler will display a fault code to help identify the problem quickly.
Short on time?
The quickest, safest, and least stressful way to get your Vaillant boiler working again is to speak to a qualified Gas Safe engineer. We offer no-obligation phone consultations and quotes and cover North London, West London, Watford, Herts and Middx and nearby.
Causes of the Vaillant F75 Fault Code
The F75 fault code is most commonly caused by one or more of the following issues:
Faulty or blocked pressure sensor
The pressure sensor monitors changes in water pressure inside the system. If it becomes blocked with debris or fails electronically, the boiler cannot detect the pressure increase it expects during start-up.
Pump not operating correctly
A partially seized, stuck, or failing pump may not circulate water properly. If the pump does not create sufficient pressure movement, the F75 fault code will be triggered.
Air trapped in the system
Airlocks within the heating system can prevent proper circulation, leading the boiler to believe there is no pressure rise.
Low system pressure (less common than assumed)
While low pressure can contribute, many F75 faults occur even when the pressure gauge shows normal readings.
Electrical or PCB issues
In rarer cases, wiring faults or a failing printed circuit board (PCB) can prevent correct communication between the pump and pressure sensor.
Steps to Resolve the F75 Fault Code in a Vaillant Boiler
Important: Homeowners should only carry out basic visual checks. Internal boiler repairs must be completed by a qualified engineer.
Check the boiler pressure
The pressure gauge should usually read between 1.0 and 1.5 bar when cold. If it is below this, topping up via the filling loop may help, but this alone will not fix most F75 faults.
Bleed radiators (if safe to do so)
If air is trapped in the system, bleeding radiators may help restore circulation. Always recheck pressure afterwards.
Reset the boiler
A single reset may clear temporary faults, but repeated resets should be avoided.
Call a qualified Gas Safe engineer
If the fault returns, professional diagnosis is required. Engineers will typically check:
- Pump operation
- Pressure sensor function
- System blockages
- Electrical connections
Who can fix a Vaillant F75 Fault Code.
Only a Gas Safe registered heating engineer is legally permitted to work on gas boilers in the UK.
Boiler repairs involve gas, electrics, and pressurised systems. Incorrect repairs can result in:
- Gas leaks
- Fire or explosion risk
- Carbon monoxide exposure
- Invalidated warranties and insurance
A qualified engineer has the tools, training, and legal authority to fix the issue safely and correctly.
For additional reassurance, homeowners can verify engineers via the Gas Safe Register or consult official Vaillant support guidance.
Preventing the F75 Fault Code
While not all faults can be prevented, these steps can reduce the risk:
Monitor system pressure
Check your boiler pressure regularly and address drops early.
Annual boiler servicing
Routine servicing helps identify failing pumps, sensors, and blockages before breakdowns occur.
Keep the system clean
A power flush or magnetic filter can prevent debris buildup that affects sensors and pumps.
Conclusion
The Vaillant F75 fault code is usually caused by a pump or pressure detection issue, not simply low pressure.
Ignoring the fault or repeatedly resetting the boiler can lead to further damage. Early professional diagnosis is the safest and most cost-effective approach.
At Advanced Heating & Plumbing, our experienced engineers regularly diagnose and repair Vaillant F75 faults quickly and safely.
We provide reliable, transparent service you can trust.
Next Steps
If your Vaillant boiler is displaying the F75 fault code, take action promptly to avoid further damage.
Do not attempt internal repairs yourself, as this may be dangerous and invalidate your warranty.
Contact us today to book an appointment or arrange a no-obligation consultation.
We cover locations in London, Watford, Hertfordshire, and Middlesex.
Disclaimer: This article is provided for educational purposes only and does not replace diagnosis or repair by a certified Gas Safe engineer. Any actions taken based on this information are at your own risk. Always seek professional advice before carrying out boiler repairs or maintenance.
