BoilerFaultCodesPotterton P0.1-0.4 Fault Code
Also written as P0104 — same fault.
The Potterton P0.1-0.4 fault code means: your boiler has switched itself off because the water pressure is too low for it to run safely.. It appears on 1 Potterton model in our database.
Technical description: Boiler off because pressure too low. Replenish CH system & purge air. Find leak(s) and repair.
What causes the Potterton P0.1-0.4 fault?
This fault occurs when the water inside your central heating system drops below the minimum level required for the boiler to operate. The most common reasons are a slow leak from a radiator valve or pipework, or a loss of air pressure inside the expansion vessel which causes water to be expelled through the safety valve.
This issue is frequently seen in autumn when the heating is turned on for the first time after summer, as joints may have contracted or weeped while cold.
DIY fix possible
Locate the two black handles on the filling loop braided hose underneath the boiler.Slowly turn both handles to the open position until you hear water entering the system.Watch the pressure gauge and close both handles once the needle reaches between 1.0 and 1.5 bar.
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Gas Safe Register →Potterton models that show the P0.1-0.4 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton P0.1-0.4 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