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Vaillant fault code

F22 Low water pressure in the system

Guidance for a fault shown on a Vaillant boiler. Read the answer first, then decide whether a safe external check is appropriate.

SeverityCaution

Visible, external checks may be appropriate. Do not open the boiler.

Answer first

What does F22 mean?

Vaillant F22 means the boiler has detected low system water pressure. If the pressure is below 1 bar and you are confident using your external filling loop, Vaillant advises repressurising to 1–1.5 bar. If the pressure is already above 1 bar, keeps falling, or you are unsure, arrange a qualified engineer instead.

Safety verdict

Do not remove the boiler casing or try to repair internal components. If you smell gas, call 0800 111 999.

Safe homeowner checks

  1. Read the pressure gauge or display without opening the boiler.
  2. If it is below 1 bar, use only the filling-loop instructions in your boiler manual if you are competent and confident.
  3. Stop if pressure rises above the normal range, water is leaking, or you are unsure what to do.
  4. If you smell gas, call 0800 111 999.

Models this may affect

  • ecoTEC plus
  • ecoTEC pro
  • ecoFIT pure
  • Other Vaillant models where F22 is shown in the product manual

Engineer diagnosis

What an engineer will investigate

  • Confirm actual system pressure and inspect for evidence of water loss.
  • Check pressure sensing and related system components.
  • Diagnose any recurring loss of pressure before recommending a repair.

Repair outcome data

Real outcome statistics will appear here.

Once enough anonymised jobs have been captured, this block will show sample size, same-day repair rate and cost bands without guessing or overstating the evidence.

Technical source: manufacturer fault-code guidance
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