Er.7 Medium

Vaillant Er.7 Fault Code

Also written as ER7 — same fault.

The Vaillant Er.7 fault code means: your boiler's internal tank that handles pressure changes is likely losing its charge or leaking, which can lead to system pressure spikes.. It appears on 1 Vaillant model in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Expansion vessel 10 l
Typical repair cost £180-300 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Vaillant models that show the Er.7 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Vaillant Er.7 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026