What does the Baxi H.01 – .21 fault code mean?

Your boiler is heating up too quickly when you try to use hot water, often because the water isn't flowing through the system fast enough.

How much does it cost to fix Baxi error code H.01 – .21?

Typical repair cost for the Baxi H.01 – .21 fault is £120-280 including labour.

Check that your main water stopcock and all isolation valves under the boiler are fully open.

Temporary error – flow temperature increasing too fast in domestic hot water (DHW) mode, insufficient circulation or sensor error.

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

Almost always a stuck diverter valve on combis.

Each noise points to a different fault.

Sludge build-up — needs flushing, not bleeding.