If you’ve ever found yourself nudging the thermostat higher because one or two radiators refuse to warm up, you’re not alone. Cold radiators are one of the most common home heating complaints, especially in older UK properties, and they can usually be resolved with a few logical steps. This guide walks you through diagnosing cold radiators, understanding basic heating zones, and deciding when simple zone valves can improve control and efficiency.
Quick checks you can do now
Before assuming anything complicated, try these quick checks that resolve many everyday heating issues, whether you’re in Bordon, Whitehill, Liphook or nearby areas such as Alton and Farnham.
- Ensure the boiler is actually running and the programmer is calling for heat.
- Check the thermostat batteries (if applicable).
- Confirm all radiator valves are fully open.
- Look for error codes on the boiler display.
If everything appears normal but radiators are still cold or uneven, move on to some methodical checks.
Understanding the causes behind cold radiators
Cold radiators are usually the result of one of three things: trapped air, poor system balance, or flow not reaching a certain part of the circuit. When homeowners call from GU35 or GU34 postcodes, these are the three things we test first.
- Top of radiator cold: usually trapped air.
- Bottom cold or lukewarm: sludge or circulation issues.
- Entire radiator cold: valve issues, balancing, or zone control problems.
Once you understand the likely cause, you can start resolving it.
Bleeding radiators to remove trapped air
Bleeding radiators is one of the simplest DIY jobs and often the key first step to eliminating cold spots. Air rises in the system, collecting at the top of radiators and preventing hot water from circulating fully.
To bleed a radiator safely:
- Switch off the heating and allow radiators to cool slightly.
- Use a radiator key to turn the bleed valve anti-clockwise.
- Hold a cloth underneath to catch drips.
- When water flows steadily, close the valve.
After bleeding a few radiators, check the boiler pressure. In many Bordon homes with sealed systems, the pressure will drop slightly after bleeding; simply top it up to the manufacturer’s recommended level (usually around 1.0–1.5 bar when cold).
Balancing your radiators for even heating (includes cold radiator zoning)
If some radiators heat quickly while others stay lukewarm, your system may be out of balance. Balancing regulates the flow of hot water so every radiator receives the right amount regardless of distance from the boiler. This is an essential step before thinking about any form of cold radiator zoning, because zoning only works properly when each radiator is already getting fair access to heat.
To balance radiators:
- Turn the heating on and allow all radiators to warm up.
- Identify radiators closest to the boiler – these usually heat fastest.
- Use the lockshield valve (usually with a white cap) to restrict flow slightly on fast-warming radiators.
- Open the lockshield more on radiators furthest away.
- Make small adjustments and allow 10–15 minutes between each test.
A properly balanced system should warm every radiator at roughly the same rate, even in larger homes around GU9 or GU35 where long pipe runs are common.
What are basic heating zones and how do they help?
Heating zones allow you to control different parts of your home independently. Instead of heating the whole house when you only need warmth upstairs or in a living area, a zoned system sends heat only where you want it.
Many homeowners in Bordon and Whitehill start with simple manual zoning using radiator thermostatic valves (TRVs). TRVs are helpful but limited, because they only control individual radiators rather than sections of the system. True zoning uses valves installed on the pipework to control entire floor levels or groups of rooms.
Benefits of basic zoning include:
- Reduced gas usage by avoiding unnecessary heating.
- Improved comfort, especially in larger homes.
- More precise control over daily heating schedules.
However, zoning cannot compensate for poorly performing radiators, so bleeding and balancing come first.
Installing simple zone valves for better control
If you want straightforward heating zones without upgrading your whole boiler or controls system, simple motorised zone valves can be added to your existing pipework. These electrically operated valves open or close automatically depending on the thermostat or programmer settings for that zone.
Typical examples include:
- Upstairs/downstairs zoning for two-storey homes in GU35 and GU34 areas.
- Living area/night-time zone splits.
- Extensions that benefit from independent control.
Zone valves are usually installed near the main heating manifold or pipe junctions, and wiring them into your existing controls allows each zone to operate independently. Homeowners often notice improved boiler efficiency because the system no longer needs to circulate water unnecessarily around the entire property.
Before installing zone valves, your engineer will check:
- Existing pipe layout.
- Boiler compatibility.
- Condition of radiator valves and TRVs.
- How well the system is already balanced.
This ensures the zoning upgrade works reliably and does not introduce new flow restrictions.
Checklist: When should you consider adding zones?
Consider basic zoning if:
- You frequently heat the whole house when using only one or two rooms.
- Your property has areas that warm up much faster than others.
- You have extended your home and want better control over different areas.
- You are already addressing cold radiator zoning issues such as flow balance or trapped air.
Adding zones does not replace good system maintenance, but it can significantly improve long‑term comfort.
Putting it all together for a more efficient heating system
In most homes around Bordon, Whitehill, Liphook and the wider GU areas, the solution to cold radiators is a combination of bleeding, balancing and improving flow control. Once the basics are correct, simple heating zones can provide a big step forwards in comfort and efficiency. Whether you want to understand cold radiator zoning or plan future upgrades, these steps form a strong foundation.
For friendly professional help with heating issues or system zoning, call us on (01420) 558993.