Intergas Boiler Error Code F018
F018 means the flue gases cannot escape properly or too little air can reach the boiler. You can remove a visible blockage outside yourself; if the warning keeps returning, an installer must check the flue system.
Applies to: Intergas Xtreme
Common causes
- Blockage in the flue outlet, for example from dirt, a nest or ice
- Blockage in the air inlet to the boiler
What to check, in order
- Check outside whether the flue outlet and the air inlet are clear, and remove visible blockages such as leaves.
- Reset the boiler once and check whether it starts again.
- If the code returns, have an installer check and clean the flue and inlet from inside.
Clear the code and test
- Fix what the checks above found first — pressure topped up, a radiator bled, the thermostat set right. Resetting without fixing the cause only brings the code back.
- Make sure the boiler has power and the gas tap at the boiler is open.
- If the water pressure is below 1.5 bar, top it up to between 1.5 and 2 bar with the filling loop, as your manual shows.
- Press the reset button once and watch a full cycle: the boiler should start, heat the radiators or the tap water, and keep running without the code coming back.
When to call a professional
Most cases are solved by the checks above. Book a technician if any of these apply:
- The code comes back after you have run the checks and a test cycle.
- You smell burning, see sparks or scorch marks, or the breaker trips.
- Water is leaking and you cannot stop it.
- The fix needs panels opened beyond what your manual describes, or a part tested with a meter, and you are not set up for that.
When you call, give the brand, the code F018, your model number (on a label on the type plate, usually at the bottom or on the side of the boiler) and the checks you already ran. It shortens the visit.
Parts that may be involved
Flue outlet
Parts are model-specific. Find your model number first — usually on a label on the type plate, usually at the bottom or on the side of the boiler — and match the part to that number before ordering.
Questions people ask about F018
What does F018 mean on a Intergas boiler?
F018 means: Flue outlet and/or air inlet blocked. F018 means the flue gases cannot escape properly or too little air can reach the boiler. You can remove a visible blockage outside yourself; if the warning keeps returning, an installer must check the flue system.
Can I fix Intergas F018 myself?
Start yourself: the checks on this page cover the causes you can reach without opening the machine up. If they point to a faulty part, testing or replacing it is usually a technician job.
How do I clear Intergas F018?
Fix what the checks above found first — pressure topped up, a radiator bled, the thermostat set right. Resetting without fixing the cause only brings the code back. Make sure the boiler has power and the gas tap at the boiler is open. If the water pressure is below 1.5 bar, top it up to between 1.5 and 2 bar with the filling loop, as your manual shows.
Sources checked
- Intergas HRE Parameter List / Fault Finding (manufacturer document)
- Warmgarant: Intergas storingscodes
The meaning and checks for this code were checked against the sources above in November 2026. Codes vary by model and region; if your manual lists a different meaning for your exact model, follow the manual.