Vaillant help
I'm a Vaillant approved partner and I work on these boilers most weeks, so these are the codes I get called about most. A couple you can safely sort yourself in ten minutes. The rest mean the boiler needs a professional, and repeated resets won't change that.
Smell gas? Stop here. Open windows and doors, don’t flick switches, and call the National Gas Emergency line free on 0800 111 999 before anything else.
Note the exact code down, try one reset at most, and never take the case off the boiler. Everything behind the case is Gas Safe territory by law. If you ever smell gas, skip everything below and call the National Gas Emergency line on 0800 111 999 first.
Low water pressure. The system has dropped below about 0.5 bar.
Safe to sort yourself: top the system up to around 1.2 bar using the filling loop. My boiler losing pressure guide walks through it. If F22 keeps returning, there's a leak to find.
Big temperature difference between the flow and return pipes, usually circulation.
Points at a struggling pump or restricted flow, often sludge. Engineer job.
Temperature rising too fast, again usually circulation or a blockage.
Same family as F23. Check the pressure is around 1.2 bar, then it's one for me.
Flame detected when there shouldn't be one, a sensor or gas valve issue.
Straight to an engineer. Don't keep resetting this one.
The boiler failed to ignite when starting up.
Check other gas appliances work and any prepayment meter has credit. In freezing weather check the condensate pipe isn't frozen. One reset. If it returns, it's ignition parts or gas supply, an engineer job.
The flame went out during operation.
Same checks as F28: gas supply, meter credit, frozen condensate in winter. Recurring F29 needs proper fault-finding.
Gas supply fault.
Check the gas meter and other appliances. If supply looks fine, the boiler needs a Gas Safe engineer to investigate. Never poke at gas valves yourself.
The pump ran but the boiler didn't sense the pressure change. Pump or pressure sensor.
The best-known ecoTEC code. Sometimes eased briefly by topping pressure up, but the sensor or pump needs replacing properly. Book it in before it leaves you without heating.
I’m Jamie, a Gas Safe registered engineer (No. 977838) in Burgess Hill. I handle boiler and heating repairs in Burgess Hill and across Mid Sussex, Mon to Fri with some evenings.
FAQ
One reset is reasonable. After that you're masking the fault, stressing components, and on ignition faults the boiler will eventually lock out hard anyway. Note the code and get it diagnosed.
No, I work on all the major makes including Worcester Bosch, Ideal and Baxi. Vaillant approved partner just means extra manufacturer training and backing on that brand.
If it's in warranty, a manufacturer engineer may be your cheapest route and I'll tell you so. An annual service, which I can do, is usually what keeps that warranty valid in the first place.
Get a quote
Send me a few details, and a photo of the boiler if you can. I'll get back to you quickly with a clear, no-obligation quote and honest advice.
