Vaillant boilers covered on this site
Vaillant is one of the most common boiler brands in UK homes, and most of the Vaillant boilers we get asked about are from the ecoTEC range. That includes the ecoTEC plus (available as a combi, system or regular boiler), the ecoTEC pro (a combi popular in flats and smaller homes) and the ecoTEC exclusive (a high-efficiency combi with a larger display). Fault codes are broadly shared across the range, so an F28 on an ecoTEC pro usually means the same as an F28 on an ecoTEC plus. Details vary between models, so check the code against your manual.
Where the fault code appears
On most ecoTEC models the fault code shows on the digital display on the front of the boiler as the letter F followed by two digits, for example F22 or F75. Newer models with a larger display may also show a short text description. Write the code down exactly as it appears, as it saves an engineer time.
How to reset a Vaillant boiler safely
Many faults need a manual reset once the cause has been dealt with, and the method depends on the model. Older ecoTEC boilers usually have a dedicated reset button, while some newer models use a mode button or a menu option instead. Your user manual will show which applies to your boiler.
- Deal with the likely cause first, such as low pressure or a gas supply problem.
- Press reset once and give the boiler a few minutes to try to light.
- Stop after two or three attempts. If the code keeps coming back, call a Gas Safe registered engineer.
Never remove the casing to look for the problem yourself. Everything behind the front panel is a job for a qualified engineer.
Reading the pressure gauge
Depending on the model, pressure shows on a dial gauge under or on the front of the boiler, or as a number on the display. With the heating cold, pressure should usually sit between 1 and 1.5 bar. It rises a little when the system is hot, which is normal. If it falls well below 1 bar you may see the F22 fault code. Our guide on how to repressurise a boiler walks through using the filling loop step by step.
Common winter faults
The condensate pipe carries water away from the boiler and often runs outside, so in a hard frost it can freeze solid. When that happens the boiler can lock out, and on many ecoTEC models this shows up as an ignition fault such as F28. Thawing the pipe with warm (not boiling) water is a safe job for a homeowner, and our frozen condensate pipe guide explains how. Pressure also tends to drop during long spells of heavy heating use, or after bleeding radiators, which puts F22 near the top of the list in winter.
Vaillant fault codes we cover
- F22: low water pressure, usually fixed by topping up through the filling loop.
- F28: ignition failure on start-up, often a gas supply problem or a frozen condensate pipe.
- F29: flame loss during operation, where the flame goes out after the boiler has lit.
- F75: no pressure rise when the pump starts, usually a pump, sensor or air problem.
When to call an engineer
If you smell gas, turn off the supply at the meter if it is safe to do so, open doors and windows, and call the National Gas Emergency Service on 0800 111 999. For anything beyond the basic checks above, or if a fault returns after two or three resets, book a Gas Safe registered engineer. A yearly service catches many of these problems early. See our boiler service cost guide for what a service includes and what it typically costs.