Why Aren’t My Radiators Heating Up Properly — And How Do I Fix It?

When you switch on your heating, you expect your radiators to warm up quickly and evenly. But if they’re taking ages to heat, only getting warm at the top or bottom, or staying cold altogether, there’s usually an underlying issue. Below, we’ll walk you through the most common reasons your radiators aren’t heating properly and what you can do to get things running smoothly again.

1. There’s Air Trapped in Your Radiators

If the top of your radiator feels cold while the bottom is warm, trapped air is the likely culprit.
This stops hot water from circulating properly.

Solution: Bleed Your Radiators

Bleeding releases the trapped air.
You’ll need:

• A radiator key

• A cloth or small bowl

Turn the key slowly until you hear air escape, then close it when water starts to dribble out.

If you’re unsure or don’t feel confident, we can bleed your system and check for further issues.

2. Your Radiators Need Balancing

If some radiators heat up perfectly but others in the house stay cooler, especially those furthest from the boiler, your system may be unbalanced.
This means hot water isn’t being distributed evenly.

Solution: Balance the System

Balancing involves adjusting the valves (usually the lockshield valves) to ensure water flows evenly around your home.
It’s a more technical job, so many homeowners prefer to call a heating engineer.

At Total Energy Services, we can balance your radiators as part of a system health check.

3. Sludge or Debris Is Blocking Your Radiators

Over time, rust, scale and dirt build up at the bottom of radiators.
This creates cold patches, reduced heat output and slow warm-up times.

Solution: Powerflush or Chemical Clean

We use specialist machines to flush out sludge and debris, restoring efficiency to your heating system.
A cleaner system:

• Heats up faster

• Uses less energy

• Reduces strain on the boiler

If the problem is severe, a powerflush is usually the best option.

4. Thermostatic Radiator Valves (TRVs) Are Stuck

TRVs can jam — especially during warmer months when they’re not used.
A stuck pin can stop hot water entering the radiator.

Solution: Free or Replace the TRV

Sometimes a gentle tap helps, but often the valve needs repairing or replacing.
We can supply and fit modern, efficient TRVs that give you more control over your heating.

5. Low Boiler Pressure

If your boiler pressure is too low, your radiators may take forever to warm up — or not heat at all.

Solution: Re-Pressurise the Boiler

Check the pressure gauge.
Most boilers should be set between 1 and 1.5 bar when cold.
If it’s low, you can top it up using the filling loop.

If pressure keeps dropping, that’s a sign there’s a leak or another system fault — and you’ll need an engineer to investigate.

6. Your Boiler Needs a Service

If everything else seems fine but the heating is still weak or slow, the boiler itself may be struggling.

Common signs include:

• Kettling noises

• Intermittent heating

• Poor hot water flow

• Boiler constantly cutting out

Solution: Book an Annual Boiler Service

A yearly service keeps your boiler running safely and efficiently.
Our Gas Safe and OFTEC engineers check all components, clean internal parts and ensure the boiler is working at its best.

7. The System Is Old or Undersized

If your heating system is more than 15–20 years old, or the radiators are too small for the rooms they heat, you’ll naturally get poor performance.

Solution: Consider Upgrading

Upgrading radiators or your boiler can massively improve energy efficiency and comfort — especially if you have an older oil or gas system.

We install:

• Worcester Bosch & Grant oil boilers

• Vaillant & Glow-worm gas boilers

All fitted by fully qualified, insured, DBS-checked engineers.

When to Call a Professional

While many of these issues are simple, some signs mean you should call an expert:

• Radiators still cold after bleeding

• Repeatedly low pressure

• Leaks around valves or pipework

• Boiler making unusual noises

• Heating taking more than 30 minutes to warm up

Our team at Total Energy Services covers Dorset, Wiltshire, Hampshire and Somerset, offering fast and reliable heating repairs, servicing and boiler replacements.

Need Help Getting Your Radiators Working Properly?

We can diagnose and fix the issue quickly — whether it’s air, sludge, valves, pressure or boiler problems.

📞 Call us: 01258 472132
🌐 Fill in an enquiry form

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