What does the Alpha 25 fault code mean?

Your boiler has shut down because it senses that water is heating up far too quickly, which usually happens due to circulation issues.

How much does it cost to fix Alpha error code 25?

Typical repair cost for the Alpha 25 fault is £150-300 including labour.

Overheat lock out - Rapid temperature rise of flue sensor

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

Each noise points to a different fault.

Sludge build-up — needs flushing, not bleeding.

Almost always a stuck diverter valve on combis.