Error F.22

Safety precautions:

- Only attempt basic checks and repressurising if you are confident and comfortable working near the boiler. If unsure, call a Gas Safe engineer.

- Turn the boiler off and allow it to cool before touching pipes or valves. Follow the boiler manufacturer’s instructions in the manual.

- If you find an active leak, isolate the mains water to your property and turn the boiler off. Do not operate the boiler with a visible leak.

- Never attempt to repair gas components, internal boiler parts, or replace sealed parts yourself.

Initial checks a homeowner can do:

1. Check the boiler display: confirm it shows F.22 and note the pressure reading (e.g. 0.1, 0.4 bar).

2. Look for visible signs of leaks: around the boiler, radiators, radiator valves, pipework, and any visible PRV discharge pipe. Also check for damp patches or drips under the boiler.

3. Think about recent work: have you bled radiators or had any heating repairs recently? That often causes the pressure to drop.

4. Check the pressure gauge on the front of the boiler (if fitted) to verify the reading.

How to repressurise the system (step‑by‑step):

1. Read the boiler handbook for your specific model to confirm the recommended cold pressure (usually around 1.0–1.5 bar for Vaillant combi boilers). Do not exceed the manufacturer’s guidance.

2. Locate the filling loop. On EcoTEC models this is usually beneath the boiler and can be a built‑in pair of grey knobs or a flexible braided hose with two isolation valves.

3. With the boiler off and cool, open the filling loop valves slowly. On some models you turn one valve 90° and slowly open the other. You should hear water entering the system.

4. Watch the pressure gauge or display while filling. Stop when pressure reaches about 1.2–1.5 bar (cold). Do this slowly — filling too fast can overpressurise the system.

5. Close both filling loop valves fully and ensure any removable hose is re‑secured or removed as required by your setup. Do not leave the filling loop open.

6. Reset the boiler if the F.22 code does not clear automatically. Consult the manual for the reset procedure (many Vaillant boilers require holding a reset button for several seconds).

7. Turn the boiler back on and observe operation. Check pressure again when the boiler has run; operating pressure will rise when hot but should not exceed safe limits (usually no higher than ~2.5 bar).

8. If you overpressurised, bleed one or more radiators to reduce pressure, checking the boiler gauge after each bleed.

When to call a professional:

- If the F.22 returns soon after repressurising (days or weeks) this indicates a leak or a failing component and you should contact a Gas Safe registered engineer.

- If you find any visible leaks, PRV discharge (water below or outside the boiler), or you cannot get pressure up, isolate the boiler and call an engineer.

- If repressurising doesn’t clear the fault even when pressure is correct, the pressure sensor, pump or other internal component may be faulty and needs a qualified technician.

What the engineer will check (for your information):

- Inspect for leaks in radiator valves, pipework, and at the boiler and PRV.

- Test the expansion vessel and pressure relief valve and repair or replace as required.

- Check pressure sensor, pump and electrical connections inside the boiler.

- Pressure test the system and carry out any necessary repairs and safe restoration.

Final notes:

- Repressurising the system is a straightforward temporary fix if the cause is simply low pressure, but repeated drops are not normal and need professional diagnosis.

- Never attempt internal boiler repairs or gas work yourself; always use a Gas Safe registered engineer for those tasks.