Boiler
F.75
The F.75 error code on a Worcester Bosch boiler indicates a fault with the pressure sensor or pump — it’s one of the most common Worcester Bosch faults and means your boiler has shut down as a safety precaution. Left unresolved, you’ll have no heating or hot water.
What does this error mean?
F.75 means the boiler’s internal pressure sensor has failed to detect a rise in pressure when the pump starts up. Worcester Bosch boilers expect to see a small pressure increase within seconds of the pump activating — if it doesn’t happen, the boiler locks out. This usually points to a faulty pressure sensor, a seized or failing pump, or a combination of both.
Est. repair cost
£150–£300 for pressure sensor replacement; £200–£400 for pump replacement — both including Gas Safe engineer labour
🔍 Likely causes
🛠️ Step-by-step fix
Check the pressure gauge on your boiler — it should read between 1 and 1.5 bar when cold. If it’s below 1 bar, repressurise the system using the filling loop (consult your boiler manual for the exact procedure for your model).
Once pressure is correct, press and hold the reset button on your Worcester Bosch boiler for 3–5 seconds until the display resets, then wait to see if the boiler fires up successfully.
If the error returns immediately after reset, bleed your radiators to release any trapped air, then re-check and top up the pressure if it has dropped again.
Check that none of the lockshield or thermostatic valves on your radiators are fully closed — restricted flow can trigger F.75. Open any that are fully shut.
STOP HERE: Do not attempt to replace the pressure sensor, pump, or any internal boiler components yourself. Gas boilers must only be serviced or repaired by a Gas Safe registered engineer — it is illegal and dangerous to do otherwise.
If the above steps do not resolve the fault, call a Gas Safe registered engineer. The F.75 fault is well-known to Worcester Bosch engineers and is straightforward to diagnose with the right tools.
📞 When to call a professional
If the boiler continues to display F.75 after you’ve checked the pressure and performed a reset, stop and call a Gas Safe registered engineer — do not repeatedly reset the boiler as this can mask a worsening fault. Tell the engineer you have a Worcester Bosch boiler displaying error code F.75, and mention whether your system pressure was low or normal, as this will help them diagnose quickly. Never attempt to open the boiler casing or replace internal parts yourself.
⚖️ Repair or replace?
A pressure sensor replacement typically costs £150–£300 including labour; a pump replacement runs £200–£400 depending on your boiler model and engineer’s rates. If your Worcester Bosch boiler is under 10 years old and otherwise reliable, repair is almost always worth it. If the boiler is over 12–15 years old and has had repeated breakdowns, a new Worcester Bosch or equivalent A-rated combi boiler (typically £1,800–£3,000 installed) is likely the more cost-effective long-term choice.