Late September is when London heating systems get their first real test in months. The mornings turn cold, someone turns the thermostat up, and one radiator stays stone cold. Or the boiler pressure drops, or a pipe under the floor starts to drip. If you get your heating ready for winter now, while the weather is still mild, small faults stay small. Leave it until November and you’re competing with the rest of London for an engineer. Most of it is simple: bleed radiators, check the pressure and protect the pipes.
Here’s a simple plan: what to check yourself, what to book, and what landlords are legally required to do.
Why get your heating ready for winter in September
For most of the summer, a heating system barely works. Then, within a few weeks, it runs for hours every day. That’s when weak parts show up. Air collects in radiators, valves stick, pressure drops and old joints start to leak.
Finding those problems in September means you can wait a few days for a part without sitting in a cold house. In January, the same fault can mean a week without heating.
There’s also the cost. From 1 October 2026 the Ofgem price cap rises 4% to £1,723 a year for a typical household, and gas goes up 8%. A heating system that works properly wastes less of it.
Step 1: Run the heating for an hour now
Pick a mild afternoon and put the heating on for an hour. Then walk round every room and feel each radiator, top to bottom.
- Cold at the top, warm at the bottom: there’s trapped air. The radiator needs bleeding.
- Warm at the top, cold at the bottom: usually sludge collected inside. The system may need a flush.
- Completely cold: the valve may be stuck, or the radiator may need balancing with the others.
- Some rooms warm, others not: the system is out of balance. Radiators nearest the boiler take all the heat.
Also listen. Banging, gurgling or whistling usually means air in the system, low pressure or limescale, which is common with London’s hard water.
Step 2: Bleed the radiators
To bleed radiators, you only need a radiator key. It’s the easiest way to get heating ready for winter.
- Turn the heating off and let the radiators cool.
- Hold a cloth under the bleed valve at the top corner of the radiator.
- Turn the key slowly anticlockwise until you hear air hissing out.
- Close the valve as soon as water starts to come out.
- Check the boiler pressure afterwards and top it up if it’s dropped.
When you bleed radiators, start with the one furthest from the boiler on the ground floor, then work your way up.
Step 3: Check the boiler pressure
Most combi boilers run at about 1 to 1.5 bar when cold. Below 1, many will lock out. The boiler manual shows how to top up the pressure using the filling loop.
However, if you have to top it up every few days, water is escaping somewhere. That could be a leaking radiator valve, a weeping joint under the floor or a faulty pressure relief valve. Look for damp patches on ceilings and floors, and under radiators. A small leak now is a quick repair. Ignored, it becomes a damaged ceiling.
Step 4: Book the boiler service
A gas boiler should be serviced once a year, and it must be done by a Gas Safe registered engineer. Most manufacturers need an annual service to keep the warranty valid. The engineer checks the burner, flue, gas pressure, combustion and safety devices.
Book it for September or early October. By November, many engineers are fully booked with breakdowns.
While you’re at it, test your carbon monoxide alarm. If the room with the boiler doesn’t have one, fit one. Carbon monoxide has no smell, and an alarm is the only warning you get.
Step 5: Protect pipes that could freeze
Pipes in lofts, garages, outside walls and under suspended floors are the ones that freeze first. Frozen pipes can split, and when they thaw, water pours out. Getting the heating ready for winter should include these:
- lag exposed pipes in the loft and under floors with foam pipe insulation
- insulate or cover outside taps, and turn them off from inside if you can
- find your stopcock and make sure it turns, so you can shut the water off fast
- fix dripping taps and overflows, as small drips freeze first
Landlords: what the law requires before winter
If you rent out a property, heating is your responsibility, and gas safety is a legal duty. According to the Gas Safe Register, landlords must:
- have every gas appliance, fitting and flue checked every 12 months by a Gas Safe registered engineer
- give current tenants a copy of the gas safety record within 28 days
- give new tenants a copy at the start of their tenancy
- keep each record until two more checks have been done
You can book the check from 10 months after the last one and keep the original expiry date. September is a sensible time to line it up with the boiler service.
Heating failures are also one of the most common tenant complaints in autumn. Showing tenants how to bleed radiators and fixing valves and leaks before they fail saves emergency call-outs and keeps tenants happy. Our property management support can help you keep on top of it across several properties.
How CityPrime helps get your heating ready for winter
Work on the gas boiler itself always needs a Gas Safe registered engineer. Alongside that, our plumbing team handles everything around it: leak detection and repair, radiator installation and relocation, pipework repairs, water pressure problems, and resealing. We can also lag pipes, fix sticking valves and sort the damp patches that leaks leave behind with our plastering team.
If a pipe bursts or a radiator starts leaking badly, our 24/7 emergency call-out service is there for you. And for the rest of the house, read our guide to home repairs you shouldn’t ignore this autumn.
Winter heating questions
When should I get my heating ready for winter?
Late September or early October is ideal. The weather is still mild, parts are easy to get, and engineers aren’t yet busy with breakdowns.
How do I know if my radiators need bleeding?
If a radiator is cold at the top and warm at the bottom once the heating is on, there’s air trapped inside. Gurgling noises are another sign. Bleed radiators like that, then check the boiler pressure.
Why does my boiler pressure keep dropping?
Usually because water is escaping from the system. Common causes are a leaking radiator valve, a weeping pipe joint or a faulty pressure relief valve. It’s worth getting it checked before winter.
How often does a landlord need a gas safety check?
Every 12 months. The check must be done by a Gas Safe registered engineer, and tenants must get a copy of the record within 28 days.
How can I stop pipes freezing in winter?
Lag pipes in lofts and under floors, cover outside taps, fix drips and keep the heating on low when you’re away during a cold snap.
Want leaks, radiators and pipework sorted before the cold arrives? Book online, call us on 020 3855 2692, or send us a message.
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