No heating and no hot water at all
Before assuming the boiler has failed, there are four things worth checking that account for a large share of these call-outs and cost nothing to rule out.
What it usually means
Complete loss of heating and hot water feels like the worst case, but it frequently is not. A significant proportion of these call-outs turn out to be power, pressure, gas supply or a control setting rather than a boiler fault, and all four can be checked in a few minutes without any tools.
Work through them in order. If none of them is the answer, the boiler is displaying a code or it is not — and that distinction is what an engineer will want to know first when you ring.
If the boiler is showing a code, look it up rather than guessing. The code tells you which family of fault you are in and often turns a vague emergency into a five-minute fix.
How to narrow it down
Work through these in order.
Is there power to the boiler?
Check the display is lit and the fused spur next to the boiler is switched on. Check the consumer unit for a tripped breaker or RCD. A boiler on a shared circuit can be knocked out by a completely unrelated appliance failing.
What does the pressure gauge read?
Below 0.5 bar the boiler will refuse to fire. Top up to 1.2 bar using the filling loop and reset. This alone resolves a large share of no-heating calls, especially in the first cold week of the season.
Do other gas appliances work?
If the hob will not light either, there is no gas at the property. Check the emergency control valve at the meter is in line with the pipe and check a prepayment meter for credit before calling anyone.
Has the timer or thermostat lost its settings?
A programmer that has lost its battery backup after a power cut will sit there looking normal while calling for nothing. Check the time and date are right and that the schedule has not reset to off.
Is the boiler showing a fault code?
Write down exactly what it shows, including any letters and any three-digit suffix, and look it up. The code narrows the diagnosis enormously and often points to something you can fix yourself in ten minutes.
Codes commonly shown with this
- F.22VaillantThe boiler has shut down because there is not enough water in the system. Pressure has dropped below roughly 0.5 bar and it will not fire until you top it up.Get it checked
- EA 227Worcester BoschThe boiler tried to light and never detected a flame, so it has shut the gas off and locked out. This is the most common Worcester fault code.Stop — call an engineer
- L2IdealThe boiler failed to detect a flame during ignition and has locked out on the gas valve. Do not keep resetting it.Stop — call an engineer
- E133BaxiBaxi's ignition lockout: "the gas supply has been interrupted, ignition has failed or the flame has not been detected". Check the gas is on, reset once. If it returns, stop.Get it checked
- A01VokèraThe burner failed to light and the appliance has locked out. Check the gas supply and, in cold weather, the condensate pipe before calling anyone.Get it checked
- 501AristonNo flame was detected during ignition and the appliance has locked out. Check the gas supply and the condensate pipe before booking anyone.Get it checked
When it is urgent
Take care
What it costs
Typical repair cost
£0–£450
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Get an engineer to look at this
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.