BoilerFaultCodesPotterton P19 Fault Code
The Potterton P19 fault code means: your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.. It appears on 1 Potterton model in our database.
Technical description: Low water pressure (below 0.5 bar)
What causes the Potterton P19 fault?
This fault occurs when the water level inside your central heating system drops below the minimum required for the boiler to heat up safely. The most common reasons are a small leak in your pipework or radiators, or because the expansion vessel inside the boiler has lost its air charge and can no longer regulate pressure.
This code is frequently seen when homeowners turn their heating back on for the first time in autumn, as the system settles and reveals pressure losses that occurred over the summer.
DIY fix possible
Locate the filling loop (a flexible silver hose) usually found underneath or near the boiler.Slowly open the valve(s) on the filling loop to allow water into the system.Watch the pressure gauge and close the valves tightly once the needle reaches between 1 and 1.5 bar.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Potterton models that show the P19 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton P19 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