BoilerFaultCodesYour boiler has detected that the water pressure is too low to operate safely, causing it to shut down temporarily.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Low system pressure – increase the system pressure to 0.8 bar
What causes this fault?
This fault occurs because the internal sensors have detected that there is not enough water inside the central heating system to circulate safely. The most common reason is a minor leak in the pipework or radiators, though it can also happen if air was recently bled from your radiators without the pressure being topped up.
This issue is frequently seen at the start of autumn when homeowners turn their heating back on for the first time after the summer break.
DIY fix possible
Locate the filling loop (usually a silver flexible hose) underneath or near the boiler.Slowly open the one or two taps/levers on the filling loop until you hear water moving.Watch the pressure gauge and close the taps firmly once the needle reaches 1.5 bar.
Find a Gas Safe engineer
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Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like HJ-09 — 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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