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F.22

Vaillant Boiler

Severity: Moderate

Source: OnlyErrorCodes.com — Every error code. One place.

Vaillant Boiler F.22 Error — Low Water Pressure

What it means

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

  1. 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.

  2. 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.

  3. 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.

  4. Close the filling loop fully.

    Close all valves completely after repressurising.
    A valve left slightly open allows continuous water entry or dripping.

  5. 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.