F22
Low water pressure
Repressurise to 1.0–1.5 bar. Persistent loss indicates a leak or a failed expansion vessel.
Fault code index
Vaillant Boiler Fault Codes Explained
Every common Vaillant lockout code, what it actually means, and whether it is a simple pressure top-up or a safety fault needing a Gas Safe registered engineer.
Vaillant diagnostic code matrix
F28
Ignition block — start-up failure
No gas, faulty gas valve, electrode or PCB. Check other gas appliances first, then call an engineer.
F75
Pump / pressure sensor fault
The sensor sees no pressure change when the pump starts — typically a pump or sensor replacement.
F27
Flame detected with gas valve closed
Safety shutdown. Do not reset repeatedly; requires engineer attendance.
F62
Delayed gas valve shut-off
Gas valve fault — replacement required by a Gas Safe engineer.
F29
Flame lost during operation
Interrupted gas supply, flue recirculation or ignition earth fault.
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Vaillant fault codes — FAQs
What does F22 mean on a Vaillant boiler?
- F22 indicates low water pressure. It should be diagnosed by a Gas Safe registered engineer if it returns after a single reset.
Can I clear a Vaillant fault code myself?
- Low pressure codes can usually be cleared by repressurising the system. Ignition, fan, flame and overheat codes need an engineer.
Do you carry Vaillant parts?
- We stock common Vaillant fans, pumps, sensors and electrodes, so many repairs are completed on the first visit.
Will a repair affect my Vaillant warranty?
- No. We fit genuine manufacturer-approved parts and record the work, keeping your warranty intact.
How fast can you attend a Vaillant breakdown in Warrington?
- Same-day or next-morning in most cases — we cover Warrington and the surrounding areas every day.
Vaillant boiler locked out? We can help today.
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