BoilerFaultCodesWorcester Bosch Flue Spillage Fault Fault Code
Also written as FLUESPILLAGEFAULT — same fault.
The Worcester Bosch Flue Spillage Fault fault code means: your boiler has detected dangerous exhaust fumes leaking back into the unit, which is a serious safety risk and has caused the system to shut down.. It appears on 1 Worcester Bosch model in our database.
Technical description: Flue gas detected inside boiler. Is the flue correctly installed and free of blockages?; Check air/gas channels in gas/water heat exchanger; Replace flue gas safety device.
What causes the Worcester Bosch Flue Spillage Fault fault?
This fault occurs when the boiler's internal sensors detect that poisonous exhaust gases are leaking back into the casing instead of being safely expelled outside. The most common reasons are a blockage in the flue pipe, a cracked internal seal, or heavy debris buildup within the heat exchanger that prevents the fumes from flowing away correctly.
This fault can be more frequent in autumn or winter if debris like fallen leaves or nesting birds have blocked the external flue terminal.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Search the official register for a qualified engineer in your area.
Gas Safe Register →Worcester Bosch models that show the Flue Spillage Fault fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch Flue Spillage Fault fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026