The boiler is not detecting proper water circulation, so it has shut down to protect itself.
Most common on: Baxi 600, Baxi 800, EcoBlue, Platinum+, Duo-tec
E125 means the boiler is not sensing enough water movement through the primary circuit. Firing without proper circulation would let the heat exchanger overheat, so the boiler stops. It is closely related to the overheat code but flags the circulation problem directly.
It is usually a circulation issue — a stuck or failing pump, an airlock or low pressure — rather than a fault with the burner itself. Clearing the underlying flow problem is what fixes it.
If pressure is below 1 bar, top up using the filling loop to around 1.0–1.5 bar (cold) and reset.
With the heating calling for heat, feel whether the pump is running and warm. A silent, cold pump may be seized or airlocked.
Bleeding radiators and the boiler can clear an airlock, but if the fault returns it needs an engineer to check the pump and sensors.
A failing pump, blockage or sludged system needs a heating engineer to diagnose, and may need a power flush.
Work on the gas side of a boiler must be carried out by a Gas Safe registered engineer. The checks above are limited to safe, non-invasive things a homeowner can look at (pressure, resets, the gas supply) — if in doubt, stop and call an engineer.
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The boiler is not detecting proper water circulation, so it has shut down to protect itself. E125 means the boiler is not sensing enough water movement through the primary circuit. Firing without proper circulation would let the heat exchanger overheat, so the boiler stops. It is closely related to the overheat code but flags the circulation problem directly.
You can try a single reset and the safe checks below, but Baxi E125 usually needs a Gas Safe registered engineer. Never work on the gas side of a boiler yourself — it is illegal and dangerous unless you are Gas Safe registered.
A recurring E125 means the underlying cause has not been fixed — most often seized, airlocked or failing circulation pump. Resetting repeatedly will not solve it; get the boiler diagnosed properly.
See all Baxi fault codes.