Quick answer: Baxi E125 means water isn’t circulating properly through the boiler. After the burner lit, the temperature either didn’t rise or shot up too fast, so the boiler locked out to protect itself. Low pressure and trapped air are common causes you can check yourself. A failing pump or a build-up of sludge needs a Gas Safe engineer.
E125 is the boiler telling you water isn’t moving the way it should. Sometimes that’s a simple pressure top-up. Sometimes it’s the pump wearing out. The key is not to keep resetting it, because running a boiler with poor circulation is how a pump repair turns into a heat exchanger replacement. If your Baxi is over 8 years old and out of warranty, that bigger repair bill is often the point where a new boiler fitted in Edinburgh makes more sense.
What does the Baxi E125 error code mean?
E125 is a primary circulation fault. Baxi’s fault tables call it a “water circulation fault”. The display may show just “125” with a reset symbol.
Baxi’s installer manuals explain exactly what trips it. Either the boiler temperature hasn’t risen by at least 1°C within 15 seconds of the burner lighting, or it has overshot the set temperature by 30°C twice within 10 minutes. Both point to water not flowing through the heat exchanger properly.
You’ll see E125 on Baxi Duo-tec, Platinum, Assure, EcoBlue and Megaflo boilers, and on some Potterton and Main models. The newest Baxi Combi 2 range uses a different code for the same problem.
What causes a Baxi E125 fault?
Low pressure and air cause many E125 lockouts. A worn pump or sludge causes most of the rest.
| Cause | What’s happening | Can you check it? |
|---|---|---|
| Low system pressure | Too little water to circulate properly | Yes, on the gauge |
| Air in the system | Air pockets block the flow of water | Yes, by bleeding radiators |
| Closed valves | A radiator or isolation valve has been left shut | Partly, radiator valves |
| Pump seized or failing | The pump can’t push water round the system | No, engineer |
| Sludge or debris | Build-up narrows pipes and the heat exchanger | No, engineer |
How do you fix a Baxi E125 error?
Check the pressure, bleed any cold radiators and reset once.
- Look at the pressure gauge. Baxi recommends between 1 and 2 bar. If it’s below 1, top up using the filling loop.
- Bleed any radiators that are cold at the top.
- Check the pressure again after bleeding and top up if needed.
- Make sure radiator valves are open.
- Press the reset button briefly, about 1 second on most current Baxi boilers.
If E125 comes back, stop resetting and book a boiler repair. If you have to keep topping up the pressure every few days, there’s a leak somewhere, and that needs finding too.
Is Baxi E125 serious?
It can be. The lockout itself is protective, but if the cause is left alone the boiler overheats every time it fires. Over time that can damage the heat exchanger, which is one of the most expensive parts to replace. Treat a recurring E125 as a job for this week, not next month.
Can sludge cause E125 in older Scottish homes?
Yes, sludge is a common cause in older systems. Many Edinburgh tenements and stone-built houses across the Lothians have long pipe runs and radiators that have been in place for decades. Over time, rust and debris collect as sludge and slow the water down.
If your radiators are cold at the bottom but warm at the top, sludge is a likely culprit. A power flush clears it out. A magnetic filter on the pipework keeps it from building up again.
How much does it cost to fix Baxi E125?
It depends on the cause, from nothing for a top-up to several hundred pounds for a new pump or a power flush.
| Repair | Typical UK cost |
|---|---|
| Pressure top-up and bleeding radiators | £0 |
| Minor fix and diagnosis | £80 to £200 |
| Pump replacement | £150 to £400 |
| Power flush | £350 to £800 |
| Heat exchanger replacement | £400 to £940 |
Indicative prices from published UK trade guides, 2024 to 2026. Your quote depends on the model, parts and size of your system.
Should you repair or replace a Baxi with E125?
If it’s a pump on a younger boiler, repair it. If your Baxi is over 8 years old, out of warranty and needs a heat exchanger, or a pump plus a power flush, compare the cost with a new boiler first.
A new A-rated boiler, fitted with a clean system and a magnetic filter, gives you better circulation and lower running costs, plus a fresh manufacturer warranty that’s often 7 to 10 years. Get a free new boiler quote to see how the numbers stack up.
Does regular servicing prevent E125?
Yes, a yearly service catches circulation problems early. A boiler service includes checking the pump, cleaning the magnetic filter and checking your system has enough inhibitor to slow sludge build-up.
When should you call an engineer for Baxi E125?
Call a Gas Safe engineer if E125 returns after you’ve checked the pressure and bled the radiators, or if you’re topping up the pressure more than once or twice a year.
Baxi Boiler Repairs Across Edinburgh and Scotland
The Edinburgh Boiler Company repairs, services and replaces Baxi boilers across Edinburgh and central Scotland. We carry out boiler repairs in Broxburn and Bonnington, boiler servicing in Livingston, and new boiler installations as far as Dunfermline and Stirling. If E125 keeps stopping your heating, our Gas Safe team can find the cause.
Frequently Asked Questions About the Baxi E125 Error
What’s the difference between Baxi E125 and E110?
E125 is a circulation fault. E110 is an overheat lockout. Poor circulation is often what causes the overheating, so E125 can lead to E110 if it’s not fixed. Our Baxi E110 guide explains more.
Can low pressure cause E125?
Yes, it’s one of the most common causes. On some Baxi, Potterton and Main boilers low pressure also shows as its own code. See our Baxi E119 guide.
Will bleeding my radiators fix E125?
It might, if trapped air is the cause. Remember to check and top up the pressure afterwards, because bleeding lets water out.
Does E125 mean my pump has failed?
Not always. Check pressure and air first. If those are fine and E125 keeps coming back, the pump is the next suspect, and an engineer can test it.
