H2o Low

Grant H2o Fault Code

Also written as H2O — same fault.

The Grant H2o fault code means: your boiler is operating normally and is simply displaying the current temperature of the water inside the system.. It appears on 1 Grant model in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Normal control panel display showing water temperature

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Grant models that show the H2o fault code

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

Source

Grant H2o fault code information on this page is sourced and cross-checked against the official Grant service / installation manuals for each affected model.

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