BoilerFaultCodesYour boiler has detected that water is slowly being lost from the system, preventing it from heating up safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: All Boilers
What causes this fault?
This fault occurs when the boiler detects a drop in system pressure, meaning there isn't enough water to circulate safely. The most common reasons are a slow leak from a radiator valve or a pipe, or a failure in the expansion vessel which helps manage pressure changes as the water heats up.
This issue often surfaces in autumn or winter when the heating is first turned back on, as the increased pressure of hot water can force leaks through weakened seals.
DIY fix possible
Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.Locate the filling loop (usually two small levers under the boiler) and slowly turn them to top up the pressure.Once the gauge reaches 1.5 bar, close the valves firmly and check if the error code clears.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like 1p3 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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