Low
S.17 on Vaillant ecoTEC sustain

Your boiler is simply finishing its cooling cycle after you have finished using hot water, and no action is required.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

DHW mode: Pump overrun

Engineer required

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

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