How much does it cost to fix Remeha error code 6.4.3 Water level control?

Typical repair cost for the Remeha 6.4.3 Water level control fault is £80-150 including labour.

6.4.3 Water level control High

Remeha 6.4.3 Water level control Fault Code

Q: What does the Remeha 6.4.3 Water level control fault code mean?

Your boiler has detected that the water pressure inside the system is critically low, so it has safely shut itself down to prevent damage.

Also written as 643WATERLEVELCONTROL — same fault.

The Remeha 6.4.3 Water level control fault code means: your boiler has detected that the water pressure inside the system is critically low, so it has safely shut itself down to prevent damage.. It appears on 2 Remeha models in our database.

Technical description: Lock out

Typical repair cost £80-150 (including labour)

DIY fix possible

Locate the external filling loop, usually two silver valves linked by a braided metal hose under the boiler.Slowly open the valves to let water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close both valves tightly and reset the boiler.

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Remeha models that show the 6.4.3 Water level control fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Remeha 6.4.3 Water level control fault code information on this page is sourced and cross-checked against the official Remeha service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026