Boiler repairs · Vaillant
Vaillant Boiler Repair: An Engineer Out Day or Night
For Vaillant boiler repair, an engineer can come out any hour for the £60 call-out, read the fault history, test the gas supply, flue and condensate route, and agree the repair price with you before any work starts. Low pressure and a frozen condensate pipe are the two faults you can often clear yourself first.
What the visit covers
- Reading the F code and the fault history stored in the boiler
- Ignition faults (F.28, F.29): electrode, gas valve, flue and condensate checks
- Pressure and pump faults (F.22, F.75): pressure sensor, pump and expansion vessel
- Fan, PCB and sensor replacement on ecoTEC and ecoFIT models
- Making the boiler safe if the part is not available tonight
Which Vaillant faults need an engineer?
Vaillant ecoTEC and ecoFIT boilers show faults as an F followed by a number. The number matters more than anything else, because it tells you whether the problem is one you can clear or one that needs the casing off.
F.22 is low water pressure. Vaillant tells owners to top up with the filling loop if the gauge reads below 1 bar, and to aim for 1 to 1.5 bar. F.75 is closely related: the boiler started its pump and the pressure sensor saw no change, which is often low pressure or air, and sometimes a failing pump or sensor. Our guide to Vaillant boiler pressure walks through the top-up.
F.28 means the boiler tried to light and never saw a flame. F.29 means it lit, lost the flame and could not relight. Both point first at the gas supply and the condensate pipe, then at the ignition electrode, gas valve or flue. Our Vaillant fault codes explained page goes through each code one by one.
F.20 (overheat cut-out), F.32 (fan), F.62 (delayed flame switch-off) and the sensor codes F.0 to F.13 are not householder faults. Reset once at most, and if the code returns, stop.
If you smell gas, do not reset anything. Open the windows, turn the gas off at the meter if you can reach it safely, use no switches, and call the National Gas Emergency Service on 0800 111 999 from outside.
Vaillant boiler not turning on: checks in the right order
Work through these before calling anyone. Each one is safe and none needs the casing opened.
- Power: is the display lit? If not, check the fused spur next to the boiler and the fuse board.
- Pressure: the gauge should read 1 to 1.5 bar with the heating cold. Below 1 bar, top up.
- Gas: do the hob and other gas appliances work? On a prepayment meter, check the credit.
- Condensate pipe: in a frost, follow the plastic pipe outside and thaw it with warm, not boiling, water.
- Controls: a flat thermostat battery or a timer set to off looks exactly like a dead boiler.
- Reset: press reset once. If the same code returns, one more try at most, then call an engineer.
What the engineer does on a Vaillant call-out
Vaillant boilers keep a short history of recent faults, and reading it is the first job. A boiler that has logged F.28 five times in a week has a different problem from one that failed once during a frost.
For ignition faults the engineer checks working gas pressure at the gas valve, inspects the ignition electrode for wear and a correct spark gap, and confirms the flue and condensate route are clear. For pressure faults they look for a leak, test the expansion vessel charge and check the pressure sensor against a gauge. Gas work is carried out by Gas Safe registered engineers.
Common Vaillant parts are widely stocked, so electrodes, sensors and many pumps can often be fitted on the first visit. A PCB or fan for an older model may need ordering. If so, the boiler is left safe and the price for the return visit is agreed before we leave. Our general boiler repair service works the same way for other makes.
What a Vaillant repair usually costs
Across the UK market, small parts such as an ignition electrode or a sensor usually cost tens of pounds, while a pump, diverter valve or fan is typically in the low hundreds, and a main PCB or heat exchanger sits at the top of the range. Labour time depends on how accessible the boiler is.
You pay the £60 call-out to get an engineer to the door. The repair price is agreed with you on site before any work starts, so you can say no if a boiler of 15 years or more is not worth repairing. Our guide on whether to repair or replace a broken boiler helps with that decision.
If your Vaillant is still inside its manufacturer guarantee, check your paperwork first. A guarantee repair may cost nothing, and it is worth knowing before you book anyone.
How the visit works
Tell us the code and the gauge reading
The F number on the display and where the pressure needle sits narrow the fault before anyone sets off.
Diagnosis at the boiler
The engineer reads the fault log, tests gas pressure and checks the flue and condensate route.
Price agreed, then the repair
You hear what failed and what it costs to fix before any work starts.
Tested and handed back
The boiler is run on heating and hot water and the pressure is left at the right level.
Vaillant fault codes we fix
Questions people ask
How many times can I reset a Vaillant boiler?
Once or twice. A reset clears a lockout after a one-off event such as a frozen condensate pipe. If the same F code comes straight back, resetting again will not fix the cause. An overheat code such as F.20 should not be reset repeatedly at all until someone knows why it tripped.
Why does my Vaillant show F.28 when it is cold outside?
The most common winter cause is a frozen condensate pipe. The water from the boiler cannot drain, it backs up, and the boiler shuts down to protect itself. Thaw the outside section with warm water, then reset.
My Vaillant pressure keeps dropping after I top it up. What is wrong?
Water is leaving the system somewhere: a weeping radiator valve, the pressure relief valve discharging outside, or a leak inside the boiler. A flat expansion vessel can also make pressure swing. Either way it needs finding, because topping up every day brings in fresh oxygenated water that corrodes the system.
Is it safe to use my Vaillant with a fault code showing?
A pressure code such as F.22 is not dangerous in itself; the boiler has stopped to protect the pump. Codes about overheating, the fan, the flue or the flame are different. Leave the boiler off and get it checked.
Can you come out at night for a Vaillant breakdown?
Yes. We work 24/7 across London and everywhere inside the M25, and the call-out is the same £60 at any hour. The repair price is agreed on site before any work starts.