Error code
Baxi Boiler Fault Code 118
Quick answer
118
System water pressure is too low
First safe action
Check the pressure gauge against the manufacturer guidance in the manual.
Meaning
Baxi boiler fault code 118 usually means the boiler has detected low system pressure and locked out to protect the heating circuit.
Likely causes
- Pressure dropped below the normal operating range
- Recent radiator bleeding or maintenance
- Ongoing water loss from a leak
Safe first checks
- Check the pressure gauge against the manufacturer guidance in the manual.
- If the boiler allows user repressurising, follow only the official filling loop method.
- Stop if pressure drops again quickly after topping up.
How to reset
- Reset the boiler only after the pressure has been restored to the correct range.
- Do not keep resetting if the pressure immediately falls again.
When to call an engineer
If pressure repeatedly drops or you notice leaks, arrange a qualified heating engineer.
Safety warning
Do not remove the boiler casing or attempt internal repairs. Use only the manufacturer-approved repressurising method, and book a qualified heating engineer if pressure keeps falling.
Useful hub links
Related fault codes
110 for Baxi Boiler
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117 for Baxi Boiler
System water pressure is too low
125 for Baxi Boiler
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128 for Baxi Boiler
Flame detection has been lost during operation
130 for Baxi Boiler
Fan, flue, or air pressure sensing problem
133 for Baxi Boiler
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Relevant guides
Frequently asked questions
Can I keep resetting a Baxi boiler with 118?+
No. If 118 returns after one standard user reset, stop there and arrange a qualified engineer if the manual gives no safe next step.
Is 118 something I can repair myself?+
Boiler faults should be treated cautiously. Stay within the user checks in the manual, and leave gas, combustion, and internal boiler repairs to a qualified professional.