Baxi E125 fault codewhat it means and how to fix it
The boiler is not detecting enough water movement through it and has stopped. Usually the pump, an air lock, or a blocked filter.
Take care
What changed just before it started?
The right answer depends on what you can see. Pick the one that matches.
Choose the option on the left that matches what your appliance is doing, and the answer for that case appears here.
First cold day of the season
A seized pump after months of standing still.
It can often be freed, but expect to replace it sooner rather than later.
Recent plumbing work
Air lock from a refill that was not vented properly.
Whoever did the work should come back and finish it.
Nothing changed — it just started doing it
Gradual restriction. The filter or the system has been silting up for a long time and has finally crossed the threshold.
Ask for the filter to be cleaned and the system water tested at the same visit.
What E125 means
E125 is a circulation failure. Baxi boilers infer flow from the difference between flow and return temperatures: if the flow side climbs rapidly while the return stays cold, water is not moving through the heat exchanger. The boiler stops rather than allow the exchanger to overheat. Pressure is often perfectly normal when this happens, which surprises people — there is plenty of water in the system, it simply is not going anywhere. Pump failure, trapped air after recent work, and a filter that has silted up completely are the three explanations that account for the great majority of these calls.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Pump failed or seized | Classic first-cold-day fault after a summer standing idle. | Common |
| Air lock | Follows a drain-down or a radiator change where the system was not vented properly. | Common |
| Blocked filter or sludged system | Radiators cold at the bottom, and a magnetic filter nobody has cleaned. | Occasional |
| Seized diverter or zone valve | Water cannot reach the circuit being called for. | Occasional |
What to try yourself
Confirm the pressure gauge reads 1.0 to 1.5 bar cold. If so, this is a flow fault, not a pressure fault.
Open all thermostatic radiator valves fully. If every valve in the house has closed, the pump has nowhere to push water.
Feel the flow pipe below the boiler as it tries to start. No warmth and no sound of circulation points squarely at the pump.
Reset once, and no more if it returns.
Repeatedly restarting a boiler that is not circulating is how heat exchangers get damaged.
Get a Gas Safe registered engineer to look at your Baxi E125
Gas Safe Register engineers only. No obligation.
What it costs to fix
Typical repair cost
£90–£700
Time on site
1h 30m
Call-out and filter clean £90–£140. Pump £280–£450. System clean £400–£700.
Typical UK prices including parts and labour, updated August 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Central heating circulating pump
CH-PUMP-15-60£90–£180Plumbing merchant
Price checked 5 August 2026
Magnetic system filter, 22mm
MAG-22£65–£120Plumbing merchant
Price checked 5 August 2026
What other owners found
Nobody has shared what worked for them on this code yet. If you have had it, you would be the first — and it genuinely helps the next person.
Related Baxi fault codes
- E110Stop — call an engineerThe overheat thermostat has tripped. The boiler is producing heat that is not being carried away, and it should stay off until that is fixed.Related: overheat and circulation
- E9 219Stop — call an engineerThe boiler has overheated and the safety thermostat has tripped. Water is not carrying heat away from the exchanger, and it should not be run until that is fixed.Related: overheat and circulation
- L1Get it checkedThe boiler is not seeing enough water flow through it to run safely, so it has stopped. Usually a pump, an air lock, or a blocked filter.Related: overheat and circulation
- E02Get it checkedThe overheat thermostat has tripped. Almost always this means water is not moving through the appliance properly rather than that it is running too hot.Related: overheat and circulation
- F.20Stop — call an engineerThe overheat thermostat has tripped because the boiler got too hot. It has shut down to protect itself and it should not be restarted repeatedly.Related: overheat and circulation
- A02Get it checkedThe safety limit thermostat has tripped on overheat. In practice this nearly always means water has stopped circulating properly.Related: overheat and circulation
Related guides
Common questions about Baxi E125
Why does it say no flow when the pressure is fine?
Pressure and flow are different measurements. Pressure says there is water in the system; flow says it is moving. A dead pump on a perfectly pressurised system produces exactly this fault, and topping up will not touch it.
Can a magnetic filter really block the whole system?
Yes, and it is the price of never servicing it. The filter is doing its job by collecting magnetite. Once it is full, everything it collected is sitting in the flow path. They are designed to be cleaned annually.
How much is the repair?
A pump is £280 to £450 fitted. Clearing an air lock or cleaning a filter is usually within a standard call-out at £90 to £140. A full clean, if the system needs it, is £400 to £700.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
- Interviews with working engineers
Checked by Technical reviewer (Gas Safe registration to be displayed on appointment) on 5 August 2026.