How much does it cost to fix Baxi error code E78?

Typical repair cost for the Baxi E78 fault is £140-£220 including labour.

E78 High

Baxi E78 Fault Code

Q: What does the Baxi E78 fault code mean?

Your boiler has lost the ability to measure the water pressure accurately, which has caused it to stop running for safety.

The Baxi E78 fault code means: your boiler has lost the ability to measure the water pressure accurately, which has caused it to stop running for safety.. It appears on 27 Baxi models in our database.

Technical description: Water pressure sensor fault

What causes the Baxi E78 fault?

This fault occurs when the internal electronic sensor responsible for monitoring water pressure fails to send a reliable signal to the boiler's main control board. The most common reason is an electrical failure within the sensor itself or loose wiring, which prevents the boiler from confirming there is enough water to operate safely.

Typical repair cost £140-£220 (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 →

Baxi models that show the E78 fault code

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

Source

Baxi E78 fault code information on this page is sourced and cross-checked against the official Baxi service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026