What does the Atag Error 18 fault code mean?

Your boiler has detected that the water inside the system has become dangerously hot and has shut itself down to prevent damage.

How much does it cost to fix Atag error code Error 18?

Typical repair cost for the Atag Error 18 fault is £150-£300 including labour.

maximum flow temperature exceeded

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.

Safety-critical — turn off, read this.