BoilerFaultCodesPotterton Pressure of 3 or greater Fault Code
Also written as PRESSUREOF3ORGREATER — same fault.
The Potterton Pressure of 3 or greater fault code means: your boiler has too much water inside it, which is causing the safety valve to leak or trigger to protect the system from bursting.. It appears on 2 Potterton models in our database.
Technical description: A pressure of 3 or greater indicates a fault. The safety pressure relief valve will operate.
What causes the Potterton Pressure of 3 or greater fault?
This fault occurs when there is too much water pressure in the system, often caused by the filling loop being left slightly open or a internal leak between the domestic hot water and central heating sides. It can also happen if the expansion vessel has lost its air charge, meaning there is no room for water to expand as it heats up. As a result, the pressure rises rapidly until it forces the safety valve to open and discharge water.
This issue often becomes apparent in winter when the heating is first turned on, as the increased heat causes water to expand and reveals a failing expansion vessel.
DIY fix possible
Check that the filling loop valves are fully closed and not letting in more water.Release excess pressure by bleeding a radiator into a container until the gauge reads between 1 and 1.5 bar.Check the discharge pipe outside for signs of leaking.If pressure continues to rise after bleeding, call a Gas Safe engineer to inspect the expansion vessel.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Potterton models that show the Pressure of 3 or greater fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton Pressure of 3 or greater fault code information on this page is sourced and cross-checked against the official Potterton service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026