High
F (Low system water pressure) on Saunier Duval Thema F 30 E Plus

Your boiler has stopped working because the water pressure inside the heating system has dropped too low to operate safely.

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

The green running light will change to a red flashing light and the display will flash the letter ‘F’ with the low system water pressure fault and the current system pressure.

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

Boiler keeps losing pressure

Six most common causes of dropping pressure.

Read →

Low pressure — repressurise guide

Step-by-step using the filling loop.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →