Medium
S.53 on Vaillant ecoFIT Pure 835

Your boiler has temporarily stopped because it detected an issue with the water flow through your radiators, often caused by the system being turned off or having trapped air.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Product in waiting period/operation block function due to low water pressure (flow/return spread too large)

From this model's manual
Verified against the Vaillant Ecofit Pure 830 installation & service manual, page 33.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Check that all radiator valves throughout your home are fully open.Ensure your central heating pump is running and not seized.Bleed your radiators to release any trapped air that may be restricting water flow.Restart the boiler to see if the fault clears.

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