High
DHW PUMP Slow flash on Grant Vortex 15-20

Your boiler's control computer is failing to communicate correctly with the water heating pump, which means the system cannot reliably produce hot water.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Indicates a possible fault with the PCB (relay). Replace PCB.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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