F.22
Vaillant Boiler
Severity: ModerateWhat Does This Error Mean?
F.22 means the system water pressure has fallen below 0.5 bar. Re-pressurise using the filling loop until the gauge reads 1.0–1.5 bar, then reset. If pressure drops again within days, the system has an active leak.
Affected Models
- Vaillant ecoTEC Plus
- Vaillant ecoTEC Pro
- Vaillant ecoFIT Pure
- Vaillant ecoFIT Sustain
- Vaillant turboTEC Plus
Common Causes
- Water naturally lost from the sealed heating system over months
- Radiators recently bled, releasing water from the system
- Leak in a radiator, pipe joint, or the boiler itself
- Faulty pressure relief valve discharging water intermittently
How to Fix It
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Locate the pressure gauge.
On most Vaillant ecoTEC models the pressure gauge is on the front — a round dial or digital bar reading. F.22 typically appears when pressure drops below 0.5 bar.
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Find and open the filling loop.
The filling loop is usually a braided hose with one or two valves beneath the boiler. Some Vaillant models have an internal filling device. Refer to your manual for its exact location.
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Add water until the gauge reads 1.0–1.5 bar.
Open the filling loop valve(s) slowly. Watch the gauge and stop at 1.0–1.5 bar. Do not overfill above 2.0 bar.
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Close the filling loop fully.
Close all valves completely after repressurising. A valve left slightly open allows continuous water entry or dripping.
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Reset the boiler.
Press the reset button on the boiler panel to clear F.22. The boiler should restart and resume normal heating.
When to Call a Professional
If F.22 returns within a few days after repressurising, an active leak exists in the system. A Gas Safe registered engineer should locate and repair it.
Frequently Asked Questions
Why does my Vaillant keep losing pressure and showing F.22?
A single F.22 after bleeding radiators is normal. Repeated F.22 within days means an active leak — common locations are radiator valves, pipe joints behind walls, or the pressure relief valve discharging outside.
What pressure should a Vaillant boiler run at?
Vaillant recommends 1.0–1.5 bar when the system is cold. Pressure rises slightly when hot, typically to 1.5–2.0 bar. F.22 triggers at approximately 0.5 bar or below.