BoilerFaultCodesYour boiler has detected a serious internal problem with the gas burner system, causing it to shut down for safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Burner Injector – Natural Gas Stereomatic, Type 7, Rs1/8 4.95mm
What causes this fault?
This fault occurs when the boiler detects an unexpected signal from the burner, often suggesting gas is present when it shouldn't be or a sensor is malfunctioning. It is usually caused by a failing gas valve that isn't closing properly or a faulty set of electrodes failing to monitor the flame correctly. The system shuts down immediately as a safety precaution to prevent unburnt gas from building up.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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 E00-721 — no call-out fees, no surprises.
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