Boiler losing pressure overnight
Quick summary
This guide explains common causes and safe checks related to boiler losing pressure overnight.
Safety first
- If you smell gas or suspect CO, leave the property and call 0800 111 999.
- Do not remove boiler covers or attempt gas work.
- If water is near electrics, isolate power only if safe.
Full checklist: Safety guidance
What to check (in order)
- Confirm when the problem occurs.
- Check obvious controls, valves, and settings.
- Look for visible leaks or unusual noises.
- Record pressure, temperatures, or behaviour patterns.
What the result means
- Consistent pattern → likely specific component issue.
- Intermittent behaviour → control or circulation issue.
- Visible leaks or discharge → system fault requiring repair.
What you can safely do
- Check settings and accessible valves.
- Monitor system pressure or temperatures.
- Document behaviour for diagnosis.
When to call a professional
- Repeated faults or lockouts.
- Any gas smell or safety concern.
- If the problem persists after basic checks.
Engineer notes
Use symptom pattern, temperature behaviour, and pressure changes to narrow subsystem causes.
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