High
N.319 on Vaillant ecoTEC Plus 836

Your boiler is struggling to circulate water properly because an internal valve is blocked with debris, which may stop your heating or hot water from working effectively.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

Bypass valve dirty. The unit's internal bypass valve is blocked.

From this model's manual
Verified against the Vaillant Ecotec Plus installation & service manual, page 95.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

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

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