How F75 shows up
- The boiler shuts down shortly after starting
- Code F75 appears when heating is requested
- An unusual pump noise (grinding, whistling)
- Heating works intermittently
- Hot water keeps working normally
What error code F75 means
- Blocked circulation pump — the rotor no longer turns freely, often after a long period of inactivity (end of summer).
- Air in the system — an air pocket prevents the water from circulating properly.
- Insufficient water pressure — the gauge shows a value too low for the pump to be detected as running.
- Faulty differential pressure sensor — the boiler no longer receives the flow signal, even though water is circulating fine.
- A system valve closed by mistake — after recent work or a service visit.
What you can safely check yourself
Check the pressure
The boiler gauge should read between 1 and 2 bar when cold. Below 1 bar, topping up is likely needed.
Check that the system valves are open
The valves on either side of the boiler or the pump should be in the open position.
Code still there? Call a professional
An F75 that doesn't clear after topping up often comes from the pump itself or the sensor — a licensed technician needs to step in.
Which brands does this code apply to?
This code is used as-is on Vaillant and Bulex boilers, two brands that share the same technical platform. On Junkers, Viessmann, Atlantic and Remeha boilers, an equivalent fault shows under a different code — our technician identifies the fault on site, whatever the brand.
A clear price, no surprises
A fixed 35 € call-out fee in Brussels, Wallonia and Flanders. The repair price is given to you before any work starts. Free, no-obligation quote on 0488 02 77 07.