How to Restart a Vaillant Boiler
10 October 2026
How to Restart a Vaillant Boiler
To restart a Vaillant boiler, record the fault code, check the power, controls and system pressure, then press and hold the reset control shown in your model’s manual. Many Vaillant boilers use a reset button or flame symbol that needs to be held for approximately three seconds.
A reset restarts the boiler after a temporary lockout. It does not repair low pressure, an ignition fault, a leak, a blocked condensate pipe or an internal component failure.
Quick answer: Check the display, pressure and heating controls, then press and hold the Vaillant reset button according to the manual. Wait for the ignition sequence to finish. If the boiler locks out again, stop resetting it and contact a Gas Safe registered engineer.
Before Restarting a Vaillant Boiler
Write down the complete fault code.
Check that the boiler display has power.
Confirm the programmer and thermostat are calling for heat.
Check the pressure against the range in your model manual.
Look for visible leaks around the boiler and radiators.
Check that other gas appliances are working normally.
If you smell gas, do not press reset or operate electrical switches. Ventilate the property if safe and contact the National Gas Emergency Service on 0800 111 999.
Where Is the Vaillant Reset Button?
The reset control is normally on the front interface near the display. Depending on the model, it may be labelled Reset, marked with a flame symbol or built into a control dial.
Vaillant controls vary across ecoTEC, ecoFIT and older ranges. Do not force a dial or press an unfamiliar control repeatedly. Check the user manual for the exact model.
How to Restart a Vaillant Boiler Step by Step
1. Record the fault code
Take a photograph of the display or write down the full code before pressing reset. The code may disappear after the boiler restarts, making it harder to explain the problem if it returns.
2. Check the heating controls
Set the room thermostat above the current room temperature and confirm the timer or programmer is switched on. For hot water, open a hot tap briefly if you have a combi boiler.
3. Check the electrical supply
Make sure the boiler’s fused spur is switched on and that no circuit breaker has tripped. Do not repeatedly reset a breaker that trips again.
4. Check the system pressure
Many sealed Vaillant systems operate around 1.0 to 1.5 bar when cold, but the correct range depends on the model. If the display shows F22 or the pressure is very low, the boiler may need repressurising before it can restart.
Read our verified guide to Vaillant F22 and low boiler pressure for the pressure checks and warning signs.
5. Locate the reset control
Find the Reset button, flame symbol or reset position on the front interface. If you cannot identify it, use the model manual rather than guessing.
6. Press and hold reset
Press and hold the reset control for the duration stated in the manual. On many Vaillant models, this is approximately three seconds. Release the control when the display changes or the boiler begins its start-up sequence.
7. Wait for ignition
The boiler may run its fan and pump before attempting ignition. Give it time to complete the sequence and do not keep pressing the button while it is starting.
8. Test heating or hot water
Turn on a hot tap or wait for the radiators to warm. Check the display, listen for unusual noises and look for water around the boiler and visible pipework.
9. Monitor the boiler
If the same error code returns, stop resetting the boiler. Record when it returned and arrange a professional diagnosis.
What Does F22 Mean on a Vaillant Boiler?
F22 usually indicates low system pressure. The boiler locks out because it has detected insufficient water pressure for safe circulation.
Check the gauge or digital pressure reading. If it is below the range in your manual, the system may need topping up with the correct filling loop or filling key. Do not keep adding water if the pressure falls again, because a leak or component fault may be present.
Why Will My Vaillant Boiler Not Restart?
Symptom | Possible cause | Safe next step |
|---|---|---|
Blank display | Power supply, fuse or control issue | Check the fused spur and arrange help if power is available but the display remains blank |
F22 code | Low system pressure | Check pressure and investigate recurring loss |
F28 or F29 | Ignition or flame failure | Do not repeatedly reset; call a Gas Safe engineer if it returns |
Pressure keeps falling | Leak, expansion vessel or safety valve fault | Arrange professional diagnosis |
Heating controls work but boiler does not fire | Control, sensor or ignition problem | Check the programmer and arrange an engineer if the fault remains |
Reset works briefly | Underlying fault has not been repaired | Stop resetting and record the code |
Can You Restart a Vaillant Boiler After a Power Cut?
Many Vaillant boilers restart automatically when power returns if the timer and thermostat still request heat. If the display shows a lockout code, perform one model-specific reset after checking the manual.
If the fused spur trips again or the display remains blank, do not keep replacing fuses or resetting the breaker. Arrange electrical or heating assistance.
How Many Times Should You Reset a Vaillant Boiler?
Try one reset after completing the safe checks in the user manual. If the boiler locks out again, stop resetting it and arrange an engineer’s inspection.
Repeated resets can hide a developing fault and do not repair a leaking component, failed sensor, gas-supply problem or circulation fault.
Boiler still showing a fault?
Use the verified InstantCost boiler calculator to compare current UK prices for diagnosis, servicing and replacement.
When to Call a Gas Safe Engineer
The same fault returns after one reset.
You smell gas or suspect a flue problem.
Water is leaking from the boiler or nearby pipework.
System pressure repeatedly drops or rises.
The boiler shows an ignition, fan, sensor or combustion fault.
The electrical supply trips repeatedly.
The boiler makes banging, grinding or unusual ignition noises.
You need to remove the boiler casing.
Only a Gas Safe registered engineer should work on the gas side or sealed internal components of a domestic boiler. Homeowners should use the normal controls only as described in the user manual.
How Much Does Vaillant Boiler Repair Cost?
InstantCost’s current UK heating data lists a standard engineer call-out and diagnosis at approximately £80 to £150, general fault diagnosis and repair at £90 to £280 and a full boiler service at approximately £70 to £120.
Indicative Vaillant boiler costs in the UK in 2026 | |
Service | Typical price |
|---|---|
Engineer call-out and diagnosis | £80 to £150 |
General boiler fault repair | £90 to £280 |
Full boiler service | £70 to £120 |
Minor leak repair | £100 to £250 |
Expansion vessel repair or replacement | £150 to £350 |
Prices vary by region, urgency, fault complexity, parts and whether VAT is included. Ask for an itemised quote before approving non-urgent work.
Vaillant Boiler Restart Safety
Never remove the boiler casing, adjust gas controls, bypass safety devices or attempt to repair ignition components. Do not use the boiler if the flue appears damaged or combustion products may be entering the property.
For model-specific steps, read Vaillant’s official boiler reset guidance.
Common Restart Mistakes
Resetting before recording the fault code
Ignoring low or unusually high pressure
Assuming every Vaillant model uses the same reset control
Removing the boiler cover to investigate
Continuing to reset after the code returns
Repressurising repeatedly without checking for a leak
Ignoring unusual smells, noises or water leaks
Frequently Asked Questions
How do I restart a Vaillant boiler?
Record the fault code, check the controls and pressure, then press and hold the reset control according to the model manual. Many models require approximately three seconds.
Where is the reset button on a Vaillant boiler?
It is usually on the front control panel near the display and may show a flame or reset symbol. The exact position varies by model.
Why does my Vaillant boiler keep needing a reset?
Repeated lockouts usually indicate an unresolved pressure, ignition, flame, circulation, sensor or electrical fault. Stop resetting it and arrange professional diagnosis.
Can I reset a Vaillant boiler with low pressure?
Check the pressure range in your manual first. If pressure is too low, the system may need repressurising before reset, but recurring pressure loss needs an engineer.
What does F28 mean on a Vaillant boiler?
F28 commonly relates to an ignition failure during start-up. Check the manual and arrange a Gas Safe engineer if the fault returns after the permitted reset attempt.
How much does it cost to repair a Vaillant boiler?
General UK boiler diagnosis and repair commonly costs around £90 to £280 in 2026. Parts, emergency timing and complex faults can increase the total.
Need a Vaillant boiler engineer?
Use the verified InstantCost boiler page to review costs and request a written quote for your fault code.