As winter sets in across Hampshire, nothing’s more frustrating than switching on the heating only to find your radiators cold at the bottom. Whether you’re in Bordon, Alton, Farnham or just outside GU35 and GU34, this problem can leave your home feeling chilly and uncomfortable. The good news is that many causes are straightforward to diagnose and fix yourself, and for the tougher jobs, Embassy Gas is on hand to help.
Why Do Radiators Get Cold at the Bottom?
When you notice the top of your radiator is warm but the bottom remains cold, it usually points to one of several underlying issues. Understanding these reasons helps you decide whether you can tackle the repair yourself or need to book a professional visit.
The 7 Most Common Causes
- Air Trapped in the Radiator
When air builds up inside, hot water can’t circulate properly. This is the number one culprit behind cold spots. - Sludge or Debris Build-Up
Over time, rust particles and muck sink to the bottom, blocking the water flow and reducing heating efficiency. - Imbalanced System
If radiators aren’t balanced, some get too much hot water while others barely get any. It often happens after system upgrades or adding new radiators. - Low Boiler Pressure
Insufficient pressure means the pump can’t push hot water around the system quickly enough, causing cold patches. - Pipework Blockages or Limescale
Hampshire has some hard water areas. Limescale can attach to the inside of pipes and radiators, restricting flow. - Faulty Thermostatic Radiator Valve (TRV)
A stuck or broken TRV can prevent hot water from entering your radiator correctly. - Inadequate Boiler Performance
An old or poorly serviced boiler might not produce enough heat, causing weak flow and cold spots.
DIY Radiator Bleeding: A Quick Fix
If trapped air is the issue, bleeding your radiators could restore full heat fast. Here’s how to bleed a radiator safely:
- Turn off your boiler and let the system cool for at least 30 minutes.
- Place a bowl or towel under the bleed valve at the top end of the radiator.
- Insert the radiator key or a flat screwdriver into the valve and turn it anti-clockwise until you hear a hissing sound.
- Once water starts to drip out, close the valve by turning it clockwise.
- Check and top up the boiler pressure if it’s dropped below 1 bar.
- Repeat for other radiators showing cold spots.
Bleeding can often solve mild cold-bottom issues in minutes. However, if you still have cold patches afterward, one of the other six causes may be at play.
Handling Sludge Build-Up
If radiators remain cold after bleeding, the system might need a power flush. Sludge accumulates over years, especially in older homes around Petersfield or Haslemere. Power flushing uses a machine to push high-velocity water through the system, dislodging rust and debris. While DIY flush kits exist, we recommend a professional power flush to avoid damaging your boiler or pipework.
Balancing Your Radiators
Balancing ensures each radiator receives the right amount of hot water. The process involves adjusting the lockshield valve on each radiator to regulate flow:
- Turn off the heating and bleed all radiators.
- Open all thermostatic radiator valves fully.
- Using an adjustable spanner, turn the lockshield valve on the coldest radiator (in the furthest room) a quarter turn anticlockwise.
- Restart the heating and feel each radiator to check temperatures.
- Adjust other radiators’ lockshield valves until temperatures level out.
Balancing can be fiddly. If you’re not confident, one visit from an expert in Alton or GU35 will sort it out quickly.
Maintaining Boiler Pressure
Low pressure is often caused by leaks, recently bled radiators, or just natural pressure loss. Check the gauge on your boiler:
- If it’s below 1 bar, locate the filling loop and gently open the valves to let water in.
- Watch the gauge rise to around 1.2–1.5 bar, then close the valves tightly.
- If pressure keeps dropping, you may have a hidden leak and should contact a Gas Safe engineer.
Dealing with Limescale and Pipe Blockages
In areas like Farnham and GU34, hard water can cause limescale in the system. While chemical inhibitors help prevent build-up, existing scale may need professional removal. Embassy Gas offers a full chemical clean service and installs magnetic filters to catch particles before they cause blockages.
Checking and Replacing Faulty TRVs
Thermostatic Radiator Valves can wear out over time or become stuck in one position. To test:
- Turn the valve from 0 to maximum – you should hear a click and feel movement.
- If it feels stuck or doesn’t respond, switch off your heating and gently remove the valve head to inspect for corrosion or debris.
- Cleaning with a soft cloth may help, but a faulty TRV often needs replacement.
When to Call in the Professionals
If you’ve bled, balanced, and topped up pressure but still see cold spots, it’s time to call Embassy Gas. A Gas Safe registered engineer can:
- Perform a full power flush and chemical clean.
- Balance your entire system precisely.
- Install magnetic filters or water softeners.
- Replace or repair faulty TRVs and pipework.
- Service or upgrade your boiler for optimal performance.
The Benefits of Regular Maintenance
Regular annual servicing not only prevents cold spots but also:
- Improves heating efficiency and lowers fuel bills.
- Extends the lifespan of your boiler and radiators.
- Reduces the risk of breakdowns in the coldest months.
- Ensures compliance with warranty and insurance requirements.
Homeowners across Hampshire—from Bordon to Petersfield—trust Embassy Gas for reliable, friendly servicing that keeps their heating systems running smoothly all year round.
Stay Warm with Embassy Gas
Don’t let cold radiators spoil your comfort. If you’re in Alton, Farnham, Haslemere, GU35 or GU34, our expert engineers are ready to help. Contact Embassy Gas today for a quick diagnostic visit or to schedule your annual boiler service. We’ll get your radiators properly heating and save you money on fuel bills!
Call us now on 01420 558 993 or book online to keep your Hampshire home cosy this winter!