BoilerFaultCodesYour boiler has too much water pressure and needs some drained out to reach a safe operating level.
Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now — this fault can be dangerous if ignored.
Technical description: High system pressure – the boiler needs to discharge water down to 0.8 bar
What causes this fault?
This fault occurs when the water pressure inside your heating system rises above the safe operating limit, causing the boiler to shut down for safety. The most common reasons are that the filling loop was left slightly open after topping up the system, or an internal component like the expansion vessel has failed and can no longer manage the pressure changes.
This fault is more frequent when you first turn the heating on after summer, as the water expands when heated and can reveal underlying pressure issues or a faulty expansion vessel.
DIY fix possible
Locate a radiator bleed valve and use a key to release water into a containerMonitor the boiler pressure gauge until it drops to between 1.0 and 1.5 barEnsure the filling loop valves are tightly closed so no more water enters the system
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 HJ-08 — 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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