A21 281
FAULT CODE
Worcester Bosch
Pump Blockage / Circulation Fault
High Severity
Engineer Required
The pump is blocked, preventing proper water circulation through the system.
Step-by-Step Fix Guide
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Step 1
Do not attempt to open the boiler
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Step 2
Try restarting the boiler — sometimes a blocked pump can free itself briefly
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Step 3 Engineer only
If the fault persists, a Gas Safe engineer will need to inspect or replace the pump
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.