@6 (( Low

Worcester Bosch @6 (( Fault Code

Also written as 6 — same fault.

The Worcester Bosch @6 (( fault code means: your boiler is signalling that the water inside your heating system is contaminated with sludge or debris, which can damage the system over time.. It appears on 2 Worcester Bosch models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Water treatment in domestic heating systems
Typical repair cost £250-450 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Worcester Bosch models that show the @6 (( fault code

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

Source

Worcester Bosch @6 (( 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 7 July 2026