Vaillant Boiler F24 Error — Pump Circulation Fault

What Does This Error Mean?

F24 means the boiler has detected poor water circulation through the heat exchanger.
Either the pump isn't running, the system has air trapped, or pipes have a blockage.
Bleed your radiators (especially upstairs ones) and check that pressure is at 1.0–1.5 bar.
If F24 returns after bleeding, the pump may be seized — call a Gas Safe engineer.

Affected Models

Vaillant ecoTEC plus
Vaillant ecoTEC pro
Vaillant ecoFIT pure
Vaillant turboMAX

Common Causes

Air trapped in the heating circuit
Pump seized after a long off-period (typical in summer)
System pressure too low (related to F22/F23)
Blocked filter on the boiler return
Magnetic filter (if installed) full and restricting flow

How to Fix It

Check the pressure gauge.

Pressure should be 1.0–1.5 bar.
If lower, top up first using the filling loop (see F23 procedure).
F24 with low pressure is often actually a pressure problem — fix that and F24 may clear.
Bleed all radiators, starting upstairs.

Trapped air rises to the highest radiators in the house.
Use a radiator key to crack open the bleed valve at the top of each radiator.
Hold a cloth under the valve.
You'll hear hissing as air escapes.
Close the valve when water comes out steadily.
Top up boiler pressure again afterwards.
Try to free a stuck pump.

If your boiler hasn't run during the summer, the pump can seize.
The Vaillant ecoTEC pump has a slot on its shaft that you can turn with a flat-blade screwdriver — through the silver cap on the front of the pump body.
Power off, turn the slot a few times, power back on.
This frees a sticking pump in many cases.
Check the magnetic filter (if installed).

If you have a Magnaclean or similar magnetic filter on the system, it may be full of magnetic sludge restricting flow.
Cleaning it is a Gas Safe engineer task — the system has to be partly drained.
Add it to the service call if you're calling someone out.
Press reset and test.

Press the reset button on the boiler.
Run heating for 30 minutes.
If F24 returns, the pump itself or the heat exchanger is the issue and needs a professional.
Don't keep resetting and trying — repeated F24 events can damage the heat exchanger.

Frequently Asked Questions

Why does F24 happen first thing in autumn?

Boilers that haven't run all summer can have a pump that's seized from sitting still, plus air that's accumulated in the system from radiators.
The first heating cycle of the year exposes both.
An annual service before winter — including system bleed and pump test — prevents most autumn F24 events.

Can I keep using hot water with F24?

Most Vaillant combi boilers will still produce hot water for taps even with F24 active.
What stops is central heating — the pump fault means radiators don't get heated.
Use the heater for showers but call an engineer to fix F24 before cold weather arrives.