Error F1

Safety precautions:

- If you smell gas, leave the property immediately, do not use electrical switches or phones inside, and call the gas emergency number. Do not attempt any work on the boiler.

- Only perform the simple external checks below. Do not open the boiler casing or tamper with gas parts or internal components. Any internal repairs, component replacements or wiring work must be carried out by a Gas Safe registered engineer.

- Turn the boiler off at the programmer/controls before working on the filling loop or radiators. Allow the system to cool if it is very hot to avoid scald risk.

Initial checks a homeowner can do:

1. Read the pressure gauge. The dial is usually under the front panel and shows pressure in bar (0–4). If the needle is below 1.0 bar (often in the red zone) the boiler is genuinely low on water. Target pressure after topping up is typically around 1.0–1.5 bar (1.5 bar is commonly recommended).

2. Visual leak check. Inspect under and around the boiler, radiator valves, visible copper pipework and any boiler connections for drips, damp patches, corrosion or pooling water. If you find a clear leak, do not repressurise the system; turn the boiler off and call a Gas Safe engineer or plumber immediately to fix the leak.

3. If the gauge shows normal pressure (around 1–2 bar) but the F1 code remains, suspect a faulty pressure sensor or wiring. In that case call a Gas Safe engineer.

How to repressurise the boiler (general guidance for combi/Logic-style boilers):

1. Locate the filling loop. This is usually a small flexible braided hose or a built-in valve assembly under the boiler. If the filling loop is removable, it is often left connected; if you cannot find it consult the boiler manual or stop and call an engineer.

2. With the boiler off, slowly open the isolating valves on the filling loop (or the two small valves if fitted). Open them only a little at first and watch the pressure gauge.

3. Allow mains water to enter the system until the pressure rises to about 1.0–1.5 bar (aim for 1.5 bar but avoid over-pressurising). Close the valves fully once the correct pressure is reached. If you have a removable filling loop, re-secure or remove it according to the manual to prevent accidental opening.

4. Do not overfill. If you accidentally exceed the recommended pressure, you may need to release some pressure by slightly opening a radiator bleed valve until the gauge returns to the correct range, then re-tighten the radiator valve.

5. Restart the boiler according to the manufacturer’s instructions and reset the fault (press the reset button or follow the display prompts). Allow a minute or two for the boiler to attempt to fire. The F1 code should clear if low pressure was the only issue.

Bleeding radiators and pressure drop:

- If you recently bled radiators, you will likely need to top the system up afterwards. Bleed radiators one at a time and check system pressure between bleeds. After bleeding, repressurise to the target and reset the boiler.

Diagnostics if problem persists:

- If pressure falls again within hours or days after topping up, there is likely a leak (including small pinhole leaks), a faulty pressure relief valve (PRV) or a corroded component. Look again for damp patches and check any cylinder, pump, radiator, or pipework that you can access.

- If the gauge shows a correct pressure but F1 remains, the pressure sensor, wiring or the boiler’s PCB may be faulty. Do not attempt electrical repairs; arrange for a Gas Safe engineer to test and replace sensors or electronics.

When to call a professional:

- Call a Gas Safe registered engineer immediately if you find a visible leak, if pressure continues to fall after topping up, if you cannot locate the filling loop, if the filling loop or valves are damaged, or if the F1 code won’t clear after correct repressurisation. Also call an engineer if you suspect a faulty pressure sensor, pressure relief valve failure, corrosion, or any internal component fault.

Final note:

- Top-up and reset will often restore normal operation if the issue was simply a temporary pressure loss. However, recurring pressure loss or any evidence of leaks or component failure requires inspection and repair by a Gas Safe registered engineer to ensure the boiler and heating system are safe and reliable.