Medium
S.53 on Vaillant ecoTEC Pro 30

Your boiler is temporarily pausing its operation to protect itself because the water is not moving through the system quickly enough.

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 is within the waiting period of the modulation block/operation block function as a result of low water pressure (flow/return spread too large)

From this model's manual
Verified against the Vaillant Ecotec Pro 30 installation & service manual, page 35.
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 all your radiator valves are fully openEnsure your system pressure is at the correct level (usually between 1 and 1.5 bar on the gauge)Bleed all radiators to release any trapped air and then top up the pressure again

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