Vaillant Fault Codes — Complete UK Reference
Vaillant ecoTEC and ecoFIT boilers display F-codes on the front panel. Most fall into three families: water pressure, ignition and pump/sensor. Here is the definitive UK reference.
Step-by-step method
F22 — Low water pressure
System pressure below 0.5 bar. Top up via the filling loop to 1.2 bar cold. Repeat drops indicate a leak — see our pressure-loss guide.
F28 — Ignition failure
No flame detected after 3 attempts. Check gas supply first (does your hob light?). If yes, dirty electrodes or gas valve — Gas Safe callout £120.
F75 — Pump / pressure sensor fault
Boiler cannot detect pressure change on pump start. Usually a jammed pump or failed sensor. £180–£340 repair.
F62 / F63 — Gas valve or PCB fault
Delayed shut-off of gas valve. Do not reset repeatedly — call an engineer. PCB or gas valve replacement £280–£450.
Frequently asked questions
How do I reset a Vaillant boiler?+
Press the reset button (the flame icon with a red circle) for 1 second. Only reset twice; persistent lockouts need an engineer.
Are Vaillant boilers better than Worcester?+
Marginally — Vaillant is quieter with better modulation. Worcester wins on parts availability and installer network. Both are 10-year warranty.