When winter sets in, few things are more frustrating than finding some rooms toasty warm while others feel like an icebox. Radiator cold spots are one of the most common heating complaints for homeowners, especially in places like Bordon, Whitehill, Liphook and Alton where older homes and mixed heating upgrades are common. The good news is that many issues can be sorted with simple DIY checks before calling in a professional.
What Causes Radiator Cold Spots?
Radiator cold spots usually point to trapped air, sludge build‑up, or an unbalanced heating system. If you notice radiators warming unevenly or heating taking longer than usual, these problems may be affecting the flow of hot water around your system. Left unresolved, they can waste energy and make your boiler work harder than needed.
Quick Checks You Can Do Now
Before you reach for tools, take a moment to run through this simple checklist. It often identifies issues quickly and saves time.
- Is your boiler pressure between 1 and 1.5 bar?
- Are all radiator valves fully open?
- Do any radiators gurgle, hiss or feel patchy in temperature?
- Is the thermostat calling for heat?
- Do radiators farthest from the boiler take the longest to warm?
If you spot anything unusual, the following DIY steps will help you tackle many common causes of radiator cold spots.
How to Bleed Radiators to Remove Trapped Air
Trapped air prevents hot water from circulating properly, often causing the top of a radiator to feel cold while the bottom stays warm. Bleeding releases this air so the radiator can fill completely with hot water again.
Follow this step-by-step guide:
- Turn on your heating and wait a few minutes so you can feel which radiators have cold areas.
- Switch the heating back off to avoid circulating more air during bleeding.
- Identify the bleed valve, usually at the top corner of the radiator.
- Hold a cloth under the valve and slowly turn it anti-clockwise with a radiator key.
- Listen for hissing – this is air escaping.
- When water starts to flow steadily, close the valve again.
- Check your boiler pressure and top it up if needed.
This simple job often solves radiator cold spots immediately, especially in homes across GU35, GU34 and GU9 where older pipework can trap air more easily.
Understanding Why Balancing Matters
Even with all the air removed, your radiators may still heat unevenly. This typically means your system is unbalanced. Balancing doesn’t involve anything technical or electrical – it simply adjusts how quickly water flows through each radiator.
The radiators closest to your boiler naturally heat faster because hot water reaches them first. Those furthest away, such as in loft conversions or extensions, may stay cooler unless you restrict the flow to the nearer radiators and encourage more water to travel to the distant ones.
Step-by-Step Guide to Balancing Radiators
Balancing is detailed but very manageable for confident DIYers. Allow at least an hour, especially if you have a large home or a system with more than 10 radiators, such as many found in Farnham and larger Bordon properties.
Here’s how to do it:
- Turn on the heating and let all radiators warm up.
- Make a list of every radiator in the house, from warmest to coolest.
- Open both valves (wheelhead/TRV and lockshield) on all radiators.
- Turn the heating off and allow radiators to cool slightly.
- Start with the warmest radiator (usually nearest the boiler). Close its lockshield valve, then reopen by a quarter turn.
- Move to the next warmest radiator, opening its lockshield slightly more.
- Continue until you reach the coldest radiator, leaving its lockshield fully open.
This method gradually restricts flow through your warmest radiators so more heat is pushed through the cooler ones. Once complete, allow the system to reheat fully and check the temperature balance again. Small adjustments may be needed, but steady consistency is a good sign you’ve resolved the issue.
Checking Thermostatic Radiator Valves (TRVs)
TRVs help control room temperature by regulating how much hot water enters the radiator. If a room in your Bordon or Liphook home refuses to warm properly, a sticky TRV may be to blame.
To check:
- Turn the TRV to maximum.
- If the radiator stays cold, remove the TRV head.
- Check the small pin underneath – it should move freely when pressed.
- If it’s stuck, gently free it with a small amount of pressure.
Never remove or dismantle internal valve components. If the pin doesn’t loosen, it’s time to call a professional.
When Sludge or Debris Could Be the Cause
If your radiator cold spots are located at the bottom, the issue is more likely sludge than air. Sludge forms from rust, scale and debris inside the system and often settles in older radiators in homes around Whitehill and Alton. This blocks heat transfer and limits water flow.
Basic DIY measures won’t remove sludge entirely, but you can test for its presence:
- Check for cold patches at the bottom even after bleeding.
- Listen for glugging noises when heating starts.
- Inspect for discoloured water when bleeding radiators.
A powerflush or system cleanse may be needed, which should be carried out by a qualified heating engineer.
Maintaining a Smooth-Running System
Once your radiators are balanced and free from trapped air, you can keep things running efficiently with a few simple habits:
- Bleed radiators once or twice each heating season.
- Check boiler pressure monthly.
- Open TRVs fully at least once a month to prevent sticking.
- Have your boiler serviced annually.
These small steps help avoid energy waste and maintain comfort throughout the home.
Need a Hand from a Gas Safe Engineer?
If you’ve followed these steps but still struggle with radiator cold spots, we can help diagnose deeper system issues and get your heating running smoothly again. Book a visit at https://www.embassygas.com/book.