How much does it cost to fix Baxi error code 118?

Typical repair cost for the Baxi 118 fault is £0-120 including labour.

118 High

Baxi 118 Fault Code

Q: What does the Baxi 118 fault code mean?

Your boiler has detected that there is not enough water in the system to operate safely, causing it to shut down temporarily.

The Baxi 118 fault code means: your boiler has detected that there is not enough water in the system to operate safely, causing it to shut down temporarily.. It appears on 26 Baxi models in our database.

Technical description: Water pressure too low

What causes the Baxi 118 fault?

This fault occurs when the internal sensors detect that the water pressure has dropped below the minimum level required to circulate heat safely. The most common reason is a small leak somewhere in the central heating pipework or radiators, though it can also happen if you have recently bled your radiators without topping the system back up.

This fault is frequently seen in autumn when homeowners turn their heating back on for the first time, as the system struggles to reach pressure after a long period of inactivity.

Typical repair cost £0-120 (including labour)

DIY fix possible

Locate the filling loop (usually a silver flexible hose) underneath your boiler.Slowly open the one or two taps/valves on the filling loop until you hear water entering the system.Watch the pressure gauge until it reaches between 1.0 and 1.5 bar, then close the taps fully.

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Baxi models that show the 118 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Baxi 118 fault code information on this page is sourced and cross-checked against the official Baxi service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026