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Vaillant Boiler F.22 Error Code

Water pressure in the heating system is too low on Vaillant boilers.

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F.22
Easy DIY fix

The boiler has lost so much water pressure that it has shut itself down to protect the heat exchanger. A slow leak, a radiator that was bled recently, or water let out through the pressure relief valve are the common reasons. If it keeps happening, Vaillant's list points at the pressure sensor, the pump, the filling device or the internal expansion vessel.

Compatible models

Vaillant ecoTEC boilers. The ecoTEC pro 24 and 28 combi manual (VUW 246/5-3 and VUW 286/5-3) and the ecoTEC plus VU GB 656/4-5 A manual call it F.22, and the operating manual for current ecoTEC plus VU, VUW and VUI ../1-5 models shows F.022.

Also shown as

The current ecoTEC plus range shows this as F.022. On the ecoTEC pro the pressure figure starts flashing below 0.8 bar and the boiler stops at 0.5 bar; the older ecoTEC plus VU 656/4-5 warns below 0.6 bar and stops at 0.3 bar.

Difficulty

Most people can clear this one at home with simple checks.

Not sure you are reading the code right? See how to read Vaillant boiler codes.

Safety first: never take the casing off a gas boiler. If you smell gas, open windows, don't use light switches, turn the gas off at the meter if you can and call your gas emergency number from outside. A carbon monoxide alarm going off means the same: switch the boiler off, get fresh air and call.

How to fix Vaillant F.22

  1. Read the pressure on the display

    With the boiler cold, look at the pressure reading or the pressure symbol. Vaillant asks for at least 1 bar, with about 1.5 bar as the usual target, and says to top up once it drops under 0.8 bar.

  2. Top up with the filling loop

    Follow the filling steps in your operating manual. On combis that's the supplied filling device: connect it, open both valves slowly, watch the reading climb to around 1.5 bar (never above 2.5 bar), then shut both valves and take the filling link off. On a system boiler, use the filling point your installer showed you.

  3. Let the boiler restart

    Once there's enough pressure the boiler starts again by itself. If it doesn't, hold the reset button for more than 3 seconds.

  4. Watch it over the next few days

    Check the gauge daily for a week. Look under radiator valves, along visible pipework and at the small copper pipe that runs outside from the relief valve for drips or damp patches.

When to call a technician

If you're topping up more than once every few weeks, water is going somewhere. A Gas Safe engineer should find the leak or check the expansion vessel and relief valve rather than you refilling forever.

Parts linked to F.22

These are the parts an engineer usually checks for this code. They sit inside the sealed casing, so leave them to a Gas Safe registered engineer.

Frequently asked questions

Which Vaillant models show the F.22 code?

Vaillant ecoTEC boilers. The ecoTEC pro 24 and 28 combi manual (VUW 246/5-3 and VUW 286/5-3) and the ecoTEC plus VU GB 656/4-5 A manual call it F.22, and the operating manual for current ecoTEC plus VU, VUW and VUI ../1-5 models shows F.022.

Can I fix Vaillant F.22 myself?

Usually, yes. Most F.22 problems clear with simple checks you can do at home. Start with the first step above: read the pressure on the display.

Other Vaillant boiler codes

Last reviewed 2026-10-21. Codes and steps can vary by model; check your owner's manual.

Sources we checked