1 P4 High

Ariston 1 P4 Fault Code

Also written as 1P4 — same fault.

The Ariston 1 P4 fault code means: your boiler is struggling to move water around your heating system effectively, which is causing it to stop for protection.. It appears on 5 Ariston models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Insufficient circulation indication
Typical repair cost £120-250 (including labour)

DIY fix possible

Check all radiator valves are fully openEnsure your system pressure is set correctly between 1 and 1.5 barCheck if your thermostatic radiator valves (TRVs) are seized or blockedBleed your radiators to remove any trapped air pockets

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Ariston models that show the 1 P4 fault code

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

Source

Ariston 1 P4 fault code information on this page is sourced and cross-checked against the official Ariston service / installation manuals for each affected model.

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