What does Vaillant F22 mean?

Low water pressure / dry-fire protection — not enough water in the system to run safely.

How do I fix Vaillant F22?

Try first: Check the pressure gauge; if under 1 bar, top up via the filling loop to about 1.2 bar; Bleed any radiators that were recently worked on, then re-check pressure. If that doesn't clear it, the likely part is Expansion vessel.

Vaillant F22 Fault — What It Means & Fix Cost

⚠ This is the likely cause from the code — a Gas Safe registered engineer confirms it on site. If you can smell gas, stop and ring 0800 111 999.

✅ Try these first — they're free

Often clears it without a callout:

Check the pressure gauge; if under 1 bar, top up via the filling loop to about 1.2 bar
Bleed any radiators that were recently worked on, then re-check pressure

🔧 If that doesn't fix it

The likely cause is one of these — the engineer confirms which:

System pressure dropped
Leak on the system
Failed expansion vessel

Most likely part: Expansion vessel

⚠ Worth knowing

Repeated F22 usually points to a leak or the expansion vessel rather than just needing a top-up

Fixed repair price

£160

Part + labour, no surprise callout fee. You only pay if you go ahead.

Book a Gas Safe engineer

You pick from the 3 nearest vetted engineers. Your choice gets first refusal; if they don't take it within a few hours it moves to the next nearest automatically — and we keep you posted.

Other Vaillant fault codes

Vaillant F28Ignition failure — the boiler couldn't establish a flame at …Vaillant F75Pressure sensor or pump fault — the boiler didn't see a pres…

Vaillant F22 — what it means

✅ Try these first — they're free

🔧 If that doesn't fix it

⚠ Worth knowing

Other Vaillant fault codes