Vaillant boilers
Vaillant is a German company. Johann Vaillant founded it in 1874 in Remscheid, Germany. It’s now one of the biggest boiler makers in Europe. Its logo is a hare, which you’ll see on the front of many boilers.
In the UK, most Vaillant gas boilers carry the ecoTEC name. The main ranges are ecoTEC pro, ecoTEC plus and ecoTEC exclusive. ecoFIT pure is a newer range. Each range comes in different sizes, shown by a number in kW (kilowatts). For example, a “32 kW” model can give more hot water at once than a “24 kW” one.
Vaillant is part of the Vaillant Group. Glow-worm belongs to the same group. That’s why many Glow-worm boilers use the same fault codes as Vaillant.
How Vaillant boilers show a fault
A Vaillant fault code starts with F, then a full stop and a number. For example, F.28 or F.22. The screen may also show codes that start with S. These are status codes. They tell you what the boiler is doing, such as heating or waiting. An S code on its own is not a fault.
Vaillant says some faults can be cleared with a reset. Its manuals tell you to hold the reset button for about a second. Don’t keep resetting over and over. If the same code comes back after a couple of tries, it needs a closer look.
The codes most people see
Two codes come up far more than the rest:
- F.22 means the water pressure is too low. You can usually fix this yourself. See how to top up low boiler pressure.
- F.28 means the boiler couldn’t light. In winter, the most common cause is a frozen condensate pipe. Vaillant has its own page on this. Our guide on thawing a frozen condensate pipe walks you through it.
Other codes, such as sensor and fan faults, need an engineer. Don’t open the boiler case to look. Vaillant’s own list says which codes need its engineers and which need your installer.
Vaillant gas boiler ranges
These are the gas boiler ranges on the Vaillant website as of 21/10/2026.
- ecoTEC plus
- ecoTEC pro
- ecoTEC exclusive
- ecoFIT pure
Older Vaillant ranges
You may still find these in homes. They are no longer sold new, but many are still working.
- ecoMAX
- Turbomax
Common Vaillant fault codes
Codes can differ between models and ages of boiler. Always check the user manual for your exact model.
| Code | What it means | What you can do |
|---|---|---|
F.20 | The safety cut-out has switched the boiler off because it got too hot. | Check the pressure is 1 to 1.5 bar. Make sure radiator valves are open and bleed out any air. If it keeps happening, call your installer. |
F.22 | Low water pressure in the system. | Top up the pressure to 1 to 1.5 bar using the filling loop, slowly. |
F.28 | The boiler tried to light but no flame was detected. | Check your other gas appliances work and your prepayment meter has credit. In cold weather, check the condensate pipe outside for ice. |
F.29 | The flame went out while the boiler was running, and it couldn't relight. | Do the same checks as for F.28. If it comes back, call an engineer. |
F.35 | The air or flue pipe is blocked. | Don't keep resetting. Call a Gas Safe engineer or your installer. |
F.75 | The boiler didn't see a big enough pressure change when the pump started. | Check the pressure gauge. If it's below 1 bar, top it up. If it's already above 1 bar, call an engineer. |
Vaillant manuals
Vaillant puts its user guides and installation manuals on its own website. You can find Vaillant manuals here. You'll need your model name. The GC number helps too. Our guide shows you how to find your boiler's model and GC number.
Stay safe. You can reset a boiler, top up its pressure and thaw a frozen condensate pipe yourself. Anything inside the case is a job for a Gas Safe registered engineer.
If you smell gas, leave the building and call 0800 111 999.