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BoilerCodes
A04Vokera

Vokera A04: insufficient system water pressure

Checked against Vokera's own documentation: Vokera Vision combi user, installation and servicing instructions and 1 more source. Last reviewed October 2026. How we check

You can usually fix this

The water pressure in the heating system is too low for the boiler to run. Vokera says to check and refill the system pressure, then reset.

Recommended pressure when cold for Vokera boilers: 1.0 to 1.5 bar.

What you can safely do

  1. Let the boiler cool and read the pressure gauge.
  2. Refill through the filling loop until the gauge reads between 1 and 1.5 bar, as Vokera recommends for a cool system.
  3. Reset the boiler and check it runs normally.

Call a Gas Safe engineer if

  • The pressure keeps dropping.
  • You can see water leaking.
Find a Gas Safe engineer near you Opens the official Gas Safe Register search.

Applies to Vision and Compact A. Codes can differ between models, so check your manual.

What A04 means on each Vokera model

From Vokera's own fault tables. Your model name is usually on the front of the boiler or in the user manual.

ModelMeaning
Vision and Compact AInsufficient system water pressure

Common questions about Vokera A04

What pressure should a Vokera boiler be?

Vokera says the gauge should be set between 1 and 1.5 bar when cool, with 0.5 bar as the minimum for safe operation.

Nearby Vokera codes

See all 12 Vokera codes

Sources

Last reviewed October 2026. Spotted something that doesn't match your manual? Email hello@boilercodes.co.uk and we'll check it. How we check