The checks every London homeowner should carry out before winter — from servicing and bleeding radiators to protecting pipes from freezing.
Quick Answer
Before winter, book an annual boiler service, bleed all radiators, check system pressure is between 1–1.5 bar, insulate exposed pipework and the condensate pipe, and test your heating on a full cycle while the weather is still mild. Doing this in autumn avoids the surge in emergency boiler breakdowns that hits London every year during the first cold snap.
At a Glance
Typical Causes
Boiler not serviced in over a year, low system pressure, trapped air in radiators, uninsulated condensate pipe
Average Repair Time
Annual service takes 45–60 minutes; full pre-winter check-up 1–2 hours
Emergency?
No — this is preventative, but avoids winter emergencies
Approx. Cost Range
Annual service from £120 + VAT; full pre-winter check-up from £180 + VAT
Who Should Deal With It
A Gas Safe registered heating engineer
Domestic or Commercial
Domestic
Risk Level
Low if addressed early — high risk of breakdown if ignored
Why Winter Preparation Matters
Every year, the first genuinely cold snap in London triggers a surge in emergency boiler callouts. Systems that have been running quietly all summer are suddenly asked to work hard, and any fault that was building unnoticed — a slow pressure leak, a trapped air pocket, worn components — finally shows itself. The good news is that almost all of this is preventable with a short checklist carried out in autumn, while engineers still have availability and before you're relying on your heating every day.
1. Book Your Annual Boiler Service
A full service checks the burner, heat exchanger, seals, flue and safety devices, and confirms the boiler is running efficiently and safely. This is the single most effective thing you can do before winter — a service carried out in September or October catches problems while there's still time to fix them without an emergency callout charge or a cold house while you wait for parts.
2. Bleed Every Radiator
Air trapped in radiators is one of the most common causes of cold spots and inefficient heating. Bleeding each radiator — starting with the ones on the lowest floor — releases trapped air and lets water fill the radiator fully, restoring even heat across the room. If a radiator is cold at the top but warm at the bottom, air is almost always the cause.
3. Check System Pressure
Most sealed heating systems should read between 1 and 1.5 bar on the pressure gauge when cold. Pressure that's crept below this range is often the result of a very small, slow leak that becomes noticeable only once the system is working harder in cold weather. Topping up pressure is straightforward, but if it keeps dropping, that's worth investigating before winter rather than during it.
Common Symptoms
Causes
- 1No annual service carried out, so faults go undetected until the boiler is under full winter load
- 2Low system pressure from small, gradual leaks that only become noticeable once the heating runs constantly
- 3Trapped air in radiators, causing cold spots and reduced efficiency
- 4An uninsulated condensate pipe freezing in cold snaps, shutting the boiler down
- 5Heating left off over summer, so a fault only surfaces the first time it's switched on for winter
4. Protect the Condensate Pipe
Modern condensing boilers produce condensate that drains away through a plastic pipe, often routed outside. In freezing weather, this pipe can freeze solid, causing the boiler to shut down completely — one of the most common causes of "no heating" emergency calls during a cold snap. Insulating any external section of this pipe with purpose-made lagging before winter prevents this entirely.
5. Test the Full System
Don't wait for the first properly cold day to discover a problem. Run your heating for a full hour on a mild autumn day, checking every room reaches temperature and the boiler doesn't display any faults. This gives you time to book a repair before you actually need the heating every day.
6. Know Your Stopcock
If a pipe does freeze and burst despite precautions, knowing exactly where your stopcock is — and confirming it turns freely — can be the difference between a quick, contained fix and significant water damage while you search for it in an emergency.
When to Call a Professional
Bleeding radiators and topping up pressure are jobs most homeowners can do themselves. A full service, persistent pressure loss, or any fault code on the boiler display should be handled by a Gas Safe registered engineer. RARE's autumn PPM visits are designed specifically to catch these issues before the cold weather arrives.
Engineering Insight
How Our Engineers Diagnose It
Book an annual boiler service with a Gas Safe engineer before the weather turns cold
Bleed every radiator in the property, starting with the lowest floor
Check the boiler pressure gauge reads between 1 and 1.5 bar and top up if needed
Run the full heating system for at least an hour to confirm even heat across every room
Check the condensate pipe route and insulate any section that runs through an unheated space, garage or external wall
Test the thermostat and any smart controls are responding correctly
Preventative Maintenance
Frequently Asked Questions
Ideally in September or October, before the heating season starts and before engineers' diaries fill up with emergency breakdowns.
Talk to a specialist today.
Our Gas Safe engineers are available same-day across Central and North London. No call-out charge quoted upfront. No obligation.
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