Every safety-critical page signed off by a Gas Safe registered engineer
Find out what your fault code means.
Type the code showing on your appliance. We will tell you what it means, whether it is safe, what you can try, and what a repair should cost.
163 codes across 23 brands · no sign-up · no manuals to wade through
What has gone wrong?
Start with the appliance, then pick the brand.
Most looked up
The codes people are searching for right now.
- 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
- 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
- 5ESamsungThe machine could not empty within the time it allows. On a Samsung this is the single most common code, and the filter behind the front flap is the usual answer.Get it checked
- E15BoschThe water protection system has activated — there is water in the base of the machine. Turn the tap off and call service. Do not tilt it, whatever else you read.Stop — call an engineer
- F.75VaillantThe boiler cannot detect a rise in pressure when the pump starts, so it has locked out. Usually a failed pressure sensor or a pump that is not moving water.Get it checked
- F05HotpointThe machine cannot pump out, so the door stays locked with water inside. Hotpoint treat this as an owner job and point you at the pump filter first.Get it checked
- F1IdealSystem pressure has dropped below the minimum the boiler will run at. Topping it back up to 1.2 bar usually clears it straight away.Get it checked
- E01AlphaThe appliance tried to light and could not confirm a flame, so it has locked out. In winter a frozen condensate pipe is the most likely reason.Get it checked
- E18BoschThe machine could not pump out in the time allowed. Bosch point at the filter and the drain hose, and warn that the water you are about to release may be scalding.Get it checked
- F.28VaillantThe boiler tried to light and failed three times in a row, so it has shut the gas off and locked out. Do not keep resetting it.Stop — call an engineer
- CE 207Worcester BoschSystem water pressure has dropped too low for the boiler to run safely. Topping the system back up to 1.2 bar usually clears it in five minutes.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
The five things that actually go wrong
Codes differ between manufacturers. The faults behind them barely do — almost every code you will ever see is one of these five.
Pressure
The sealed system has lost water and the boiler will not fire without it.
Ignition and gas
The boiler tried to light and could not confirm a flame.
Overheat and circulation
Heat is being produced faster than the water can carry it away.
Fan and flue
The boiler cannot verify that combustion products are being cleared.
Sensors and electronics
A sensor or the control board is reporting a value that cannot be right.
How it works
Enter the code
Type it exactly as it appears, or as close as you can get. F.75, F75 and 75 all find the same page.
Read the answer first
One sentence at the top tells you what the code means. Below it, whether it is dangerous, what causes it, and what to try.
Fix it or get someone who can
Safe checks are written out step by step. If it needs an engineer, we say so plainly and help you find one.
Why you can trust this
Gas and electrical faults can kill people. We treat that seriously.
Signed off by a qualified engineer
Every page marked “get it checked” or “stop” is reviewed by Appliance technical reviewer, Qualifications to be displayed on appointment.
Written from source, never copied
We read manufacturer technical documentation to establish the fact, then write the explanation ourselves. How we verify.
Kept current
Safety-critical pages are re-reviewed at least every 18 months, and every page carries the date it was last checked.