High
E00---688 on Biasi Riva Compact 24S

Your boiler has detected that water isn't moving through the system properly, meaning it won't fire up to provide heating or hot water until the internal pressure sensor is triggered.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Main flow switch membrane

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer
Search the official register →

Related guides you might find useful

No hot water but heating works

Almost always a stuck diverter valve on combis.

Read →

Boiler keeps losing pressure

Six most common causes of dropping pressure.

Read →

Boiler won't turn on — 9-step checklist

Work through these before the call-out.

Read →