Low
S.25 on Vaillant ecoTEC exclusive

Your boiler is currently just finishing its standard cooling-down process after heating your water and is not experiencing a fault.

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.

What the manual says

Manufacturer manual

DHWmode:Pump/fanoverrun

From this model's manual
Verified against the Vaillant Ecotec Exclusive installation & service manual, page 53.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This status occurs when the boiler's internal computer is verifying that the pump is moving enough water and the fan is spinning at the right speed before ignition. It is essentially a safety check to ensure the heat exchanger won't overheat once the flame starts. If the display stays on this code for a long time, it usually means the pump is struggling to move water or a sensor is providing an inaccurate reading.

Engineer required

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

Find a Gas Safe engineer
Search the official register →

Avoid the next call-out bill

A cover plan would handle faults like S.25: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Related fault codes

Related guides you might find useful