Why Pre-Winter Preparation Matters
Every year without fail, the first cold snap brings a surge of emergency calls from London homeowners discovering their heating doesn't work. Boilers that haven't run since spring refuse to fire up. Radiators are stone cold. Pipes freeze and burst. Every one of these situations is preventable with a bit of preparation before the temperature drops.
At Heat-Plex, our busiest period runs from November through February, and our emergency callout volume triples during cold snaps. Many of these emergencies could have been avoided entirely with the checks outlined in this guide. Spend an hour now to save yourself a freezing night later.
Your Complete Winter Heating Checklist
1. Turn Your Heating On — Before You Need It
The single most important thing you can do is test your heating system before the cold weather arrives. In late September or early October, switch your heating on for an hour and check:
- Does the boiler fire up without any error codes?
- Do all radiators get warm?
- Is the hot water working?
- Are there any unusual noises, smells, or leaks?
If anything seems off, you have weeks to get it investigated and repaired — rather than joining the queue of emergency callouts once winter hits.
2. Check and Adjust Your Boiler Pressure
After months of inactivity, it's common for boiler pressure to drop. Check the gauge and ensure it reads between 1.0 and 1.5 bar when the system is cold. If it's below 1.0, repressurise using the filling loop.
If the pressure has dropped to zero or close to it, there may be a slow leak that needs professional attention before the system is put under the stress of daily winter use.
3. Bleed All Radiators
Air naturally accumulates in radiators over time, especially during the summer months when the system isn't in use. Trapped air creates cold spots and prevents radiators from heating fully, meaning your boiler works harder and your rooms take longer to warm up.
Start with the radiator furthest from the boiler and work your way towards it. You'll need a radiator bleed key (available from any hardware shop for under £2). Remember to check your boiler pressure after bleeding, as releasing air will cause a small pressure drop.
4. Insulate Exposed Pipes
London temperatures regularly drop below freezing between December and March, and frozen pipes remain one of the most common causes of winter plumbing emergencies. Pipes most at risk include:
- The boiler's condensate pipe, especially if it runs externally along an outside wall.
- Pipes in unheated areas: lofts, garages, under-floor crawl spaces, and outbuildings.
- Pipes on north-facing external walls.
Pipe lagging (foam insulation) is inexpensive and easy to fit yourself. For the condensate pipe, ensure the insulation is waterproof and covers the full length of any external run. A frozen condensate pipe is the single most common cause of boiler lockouts in winter — and it's entirely preventable.
5. Service Your Boiler
If your boiler hasn't been serviced in the last 12 months, book one now. A pre-winter service ensures your boiler is safe, efficient, and ready for months of heavy use. Your engineer will check for any developing faults, clean key components, and carry out a combustion analysis to verify safe operation.
Don't leave it until November or December — by then, engineers are at peak demand and waiting times increase significantly.
6. Check Your Thermostat and Controls
Test your thermostat by setting it to a temperature higher than the current room temperature. The boiler should fire up within a few minutes. Check your programmer/timer to make sure the correct schedule is set — many homeowners discover in winter that their timer is still on the summer schedule or has lost its settings after a power cut.
If you're using a basic mechanical thermostat, consider upgrading to a smart thermostat. Devices like Hive, Nest, and Tado can save you 10–15% on heating bills through intelligent scheduling and remote control.
7. Test Your Carbon Monoxide Detector
Every home with a gas boiler should have a working carbon monoxide (CO) detector, ideally one in each room with a gas appliance and one on each floor. Before winter:
- Press the test button to check the alarm sounds.
- Check the expiry date — most CO detectors have a 5–7 year lifespan.
- Replace batteries if applicable (some are sealed units with a built-in battery).
- If you don't have a CO detector, buy one immediately. They cost as little as £15 and save lives.
8. Clear the Area Around Your Boiler and Flue
Your boiler needs adequate ventilation and its flue terminal (the pipe that exits through the wall) must be clear of obstructions. Check that:
- Nothing is stored directly around the boiler — maintain at least a 30cm clearance on all sides.
- The flue terminal outside is clear of plants, debris, bird nests, or snow.
- Air vents in the room where the boiler is installed are not blocked.
9. Check for Draughts and Heat Loss
No amount of boiler efficiency matters if your heat is escaping through gaps, draughts, and poor insulation. Before winter:
- Check window and door seals for gaps.
- Add draught excluders to external doors and letterboxes.
- Check loft insulation — it should be at least 270mm deep.
- Consider secondary glazing or thermal curtains for single-glazed windows.
These measures can reduce your heating demand by 10–20%, meaning your boiler runs less and your bills are lower.
10. Know Your Emergency Plan
Despite the best preparation, emergencies can still happen. Make sure everyone in your household knows:
- Where the boiler is and how to turn it off.
- Where the gas isolation valve is (usually near the meter).
- Where the main water stopcock is (to shut off water in case of a burst pipe).
- The Gas Emergency number: 0800 111 999 (for gas leaks and CO concerns).
- Your engineer's number: for non-emergency boiler problems, keep a trusted Gas Safe engineer's details handy. (That's us — 020 7622 0444!)
What to Do If Your Heating Fails During a Cold Snap
If your boiler stops working during cold weather:
- Check the basics: Is the thermostat set correctly? Has the pressure dropped? Is there an error code? Is the condensate pipe frozen?
- Try a reset: If the boiler has locked out, try the reset button once. If it locks out again, don't keep resetting.
- Thaw the condensate pipe: Pour warm (not boiling) water over the external section of the condensate pipe. This is the most common winter fault and often resolves the issue.
- Call for help: Our emergency engineers are available 24/7 and aim to attend within 60 minutes across London.
Get Ahead of Winter
A few simple checks now can save you from a cold, stressful, and expensive emergency this winter. If you'd like professional help preparing your heating system, our Gas Safe engineers serve all London boroughs — from Battersea and Wandsworth to Kensington and Westminster.
Book a pre-winter check or explore our service plans for year-round peace of mind.