How much does it cost to fix Ariston error code UU/tt?

Typical repair cost for the Ariston UU/tt fault is £150-250 including labour.

UU/tt High

Ariston UU/tt Fault Code

Q: What does the Ariston UU/tt fault code mean?

Your boiler is struggling to detect the flow of water circulating through the system, which prevents it from igniting to provide you with heat or hot water.

Also written as UUTT — same fault.

The Ariston UU/tt fault code means: your boiler is struggling to detect the flow of water circulating through the system, which prevents it from igniting to provide you with heat or hot water.. It appears on 3 Ariston models in our database.

Technical description: Main circuit flow switch

Typical repair cost £150-250 (including labour)

Engineer required

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

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →

Ariston models that show the UU/tt fault code

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

Source

Ariston UU/tt 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 27 April 2026