Potterton E78 Fault

Potterton E78 Fault

The Potterton E78 error code indicates a water pressure sensor fault within the boiler. This sensor plays a critical role in monitoring the system’s water pressure to ensure it operates within the safe and required parameters. A fault with this sensor can lead to issues with the boiler’s performance, potentially causing it to shut down as a precautionary measure to prevent damage or unsafe conditions.

Causes of Potterton E78 Error Code

  1. Faulty Water Pressure Sensor: The sensor itself may be malfunctioning, leading to incorrect pressure readings being relayed to the boiler’s control unit.
  2. Wiring Issues: Problems with the wiring connections between the water pressure sensor and the boiler’s control board can disrupt the accurate transmission of pressure data.
  3. Pressure Fluctuations: Significant fluctuations in system pressure, whether too high or too low, can sometimes trigger a sensor fault error if the sensor cannot accurately gauge the pressure.
  4. Sludge or Debris: Accumulation of sludge or debris in the system can affect the sensor’s ability to accurately measure water pressure.

Troubleshooting and Resolving the Potterton E78 Error Code

  1. Inspect the Water Pressure Sensor: Check for any visible signs of damage to the water pressure sensor. Cleaning or replacing a faulty sensor is often necessary to resolve the issue.
  2. Check Wiring and Connections: Ensure that all electrical connections between the pressure sensor and the boiler’s control unit are secure and in good condition. Repair or replace any damaged wiring.
  3. Monitor System Pressure: Verify that the boiler’s pressure gauge is within the recommended range (usually between 1 and 1.5 bar). Adjust the system pressure if necessary.
  4. Clear Sludge or Debris: Consider having a professional flush the system to remove any sludge or debris that could be impacting the sensor’s performance.
  5. Reset the Boiler: After addressing any potential issues, try resetting the boiler to see if the error code clears and the system returns to normal operation.
  6. Seek Professional Assistance: If the E78 error persists or you’re unsure how to proceed, it’s advisable to contact a Gas Safe registered engineer. A professional can provide a more thorough diagnosis and, if necessary, replace the water pressure sensor.
  7. Regular Maintenance: To prevent future occurrences of the E78 error and other issues, ensure your heating system receives regular maintenance from a qualified technician. This can help identify and resolve potential problems early on.


The Potterton E78 error code signifies a problem with the water pressure sensor, requiring immediate attention to ensure the boiler operates efficiently and safely. While some initial checks and cleaning can be performed by homeowners, more complex issues related to sensor functionality or system pressure typically necessitate professional intervention. Regular servicing can help maintain optimal system performance and prevent similar faults.