7 Reasons Your Radiators Aren’t Heating Up Properly (And How to Fix Them)

It’s that time of year when you expect your heating to just… work.
But if your radiators are warm at the top but cold at the bottom — or worse, not heating at all — something’s not right.

At EPM, we’re often called out across Devon for exactly this. Sometimes it’s a simple fix. Other times, it’s a sign of a bigger issue brewing in your system.

Here are 7 common reasons your radiators aren’t doing their job — and what can be done to sort them.

1. Air Trapped in the System

One of the most common culprits. You’ll usually hear gurgling or notice cold spots at the top of the radiator.

The fix: Bleed your radiators using a radiator key. Let out the trapped air until water flows steadily. If you’re unsure, we’re happy to do this as part of a system check.

2. Sludge Build-Up at the Bottom

If the radiator is cold at the bottom but hot at the top, it’s likely full of sludge — a mix of rust and debris that settles in the system over time.

The fix: A professional power flush to remove the buildup and restore flow.

3. Radiator Valves Aren’t Open or Are Faulty

Sometimes it’s as simple as a closed valve, or a thermostatic radiator valve (TRV) that’s stuck closed due to age or corrosion.

The fix: Check both valves are open. If it’s a TRV issue, we can clean, free, or replace it.

4. Radiator Needs Balancing

If some rads heat up quickly and others barely warm, your system may need balancing. That’s when flow is adjusted across the system so each radiator gets its fair share of heat.

The fix: We’ll tweak the lockshield valves to equalise flow and heat distribution — especially important in larger homes.

5. Boiler Pressure Is Too Low

Low pressure means poor circulation. You’ll usually notice it if multiple radiators underperform or the whole system takes forever to warm up.

The fix: Top up your boiler pressure to around 1.5 bar (check your boiler manual first). If it keeps dropping, you may have a leak or expansion vessel issue.

6. Airlock in the Pipework

More common in systems that have been drained or partially emptied. You’ll hear bubbling or get zero heat to one section of the house.

The fix: May require draining and refilling the system, or isolating individual circuits to release the air.

7. Your System Is Outdated

If your radiators are 20+ years old or have been painted over repeatedly, they may just not be working efficiently anymore.

The fix: Consider replacing tired old radiators with newer, more efficient models — we can advise based on room size and layout.

Final Word from EPM

If your radiators aren’t keeping up with the Devon cold, don’t suffer through it.
We’re known for our fast, responsive service — whether it’s a simple valve swap or a full system flush, we’ll sort it without the wait.