The 118 error code means your Baxi boiler has detected low water pressure in the system. This safety feature stops the boiler from operating to prevent damage when pressure is too low.
At Eazy Heat we help homeowners and landlords across the UK keep their homes warm with reliable new boiler installations.
What Does the Baxi Boiler Error Code 118 Mean?
The baxi boiler error code 118 signals that the water pressure inside the heating system has fallen below the safe minimum level. Most Baxi boilers need pressure between 1 and 1.5 bar to work properly, and when it drops, the system locks out.
What Causes the Error Code 118 on Your Baxi Boiler?
The error code 118 on your baxi boiler is usually caused by low system pressure due to leaks, air in the pipes, or problems with the filling system. At a high level, anything that reduces the amount of water or creates air pockets in the heating circuit can trigger this common fault.
Persistent error codes like this one can lead to repeated engineer visits that add up quickly. Many of our customers at Eazy Heat find that investing in a new boiler installation saves money in the long term through better efficiency and fewer breakdowns.
Leaks in the Heating System
Leaks in the heating system are one of the top reasons for the 118 error code. Even small leaks in radiators, pipe joints, or the boiler itself can slowly drain water from the system over days or weeks. In older homes, corrosion in pipes or valves makes leaks more likely, especially after cold weather expands and contracts the system. Landlords often see this in rental properties where maintenance has been delayed.
How to Fix
- Locate the pressure gauge on your Baxi boiler and confirm it reads below 1 bar.
- Check all visible pipes, radiator valves, and the boiler for any drips or damp patches.
- Use the filling loop under the boiler to add water slowly until the gauge reaches 1 to 1.5 bar.
- Tighten any loose valves or call an engineer to fix larger leaks.
- Reset the boiler and monitor the pressure daily for the next week. If it drops again, arrange for a professional leak detection to find hidden issues in the system.
Air in the Heating System
Air trapped in the pipes after bleeding radiators or from automatic air vents is another frequent cause of the 118 error. When air pockets form, they reduce the effective water volume and pressure, making the boiler think there is not enough water circulating. This is common after maintenance or in systems that have not been serviced recently.
How to Fix
- Check the pressure gauge and top up if necessary using the filling loop.
- Starting with upstairs radiators, use a radiator key to bleed each one until water flows steadily without hissing air.
- Wipe up any water that comes out and close the bleed valve tightly.
- Top up the pressure again if it has dropped during bleeding.
- Reset the boiler, run the heating, and bleed again if air noises persist. Call an engineer if air keeps returning.
Faulty Pressure Relief Valve or Filling Loop
A faulty pressure relief valve or an improperly used filling loop can cause ongoing pressure loss leading to the 118 fault code. The relief valve might be stuck open or leaking slightly, while a filling loop left slightly open after use can let water escape or air enter. These issues are more common in systems that are several years old.
How to Fix
- Inspect the pressure relief valve for any constant dripping.
- Ensure the filling loop valves are fully closed after use.
- A Gas Safe engineer tests the relief valve and replaces it if faulty.
- The filling loop is checked for leaks and proper operation.
- The system is repressurised, reset, and monitored to confirm the fix holds.
If your Baxi boiler keeps showing the error code 118 despite these fixes, it may be a sign the unit is reaching the end of its reliable life. At Eazy Heat we often recommend a new boiler installation for long term peace of mind and efficiency gains.
Tired of Repeated Baxi Boiler Pressure Problems? Upgrade with Eazy Heat
If your Baxi boiler error code 118 keeps returning, even after repressurising the system, it could indicate that your boiler is becoming unreliable or that underlying components are starting to fail. While topping up the pressure may restore your heating temporarily, recurring faults often lead to repeated call-outs, higher repair costs, and the inconvenience of unexpected breakdowns when you need your heating most.
At Eazy Heat, we make replacing your boiler simple. We provide professional new boiler installations for homeowners and landlords across the UK, with a fast, hassle-free service designed around your schedule. Every installation includes a market-leading 12-year parts and labour warranty, giving you complete confidence that your new heating system is built to last.
Ready to replace your ageing boiler? Use our online boiler quotation tool to receive a clear, fixed-price quote in just a few simple steps. Once you’re happy to proceed, we’ll arrange a professional installation so you can enjoy reliable, energy-efficient heating without the stress of recurring boiler faults.
FAQs
How can I prevent the error code 118 from returning in winter?
Regular servicing and checking pressure before cold snaps can help avoid pressure related faults during high demand.
Is it safe to keep repressurising my boiler when error code 118 appears?
Occasional top ups are fine, but repeated drops mean you should have leaks investigated professionally.
Can landlords fix error code 118 themselves in rental properties?
Basic pressure top ups are okay, but professional repairs are recommended to meet legal standards.
What other error codes often appear alongside 118?
Pressure related codes like H.0201 or similar low pressure alerts frequently accompany error code 118.
Do new boilers have better pressure management than older Baxi models?
Yes, modern boilers include improved seals, sensors, and automatic features that reduce pressure faults.
