Why Are My Radiators Not Heating Properly?

Why Are My Radiators Not Heating Properly?

Common Causes and How to Fix Them

There’s nothing more frustrating on a chilly Edinburgh morning than switching on your heating and finding your radiators aren’t warming up as they should. Whether they’re completely cold or only heating at the bottom, faulty radiators can make your home uncomfortable and cost more in energy bills.

At Able Girl Plumbing, we often help customers with radiator issues that can usually be fixed quickly once the root cause is found. In this blog, we’ll walk you through the most common reasons your radiators might not be heating properly — and what you can do about it.

1. Trapped Air in the System

Symptom: Radiators are warm at the bottom but cold at the top.

This is one of the most common issues we see. Over time, air can get into your central heating system and rise to the top of your radiators, preventing hot water from circulating fully.

🛠️ Solution:
Bleed your radiators. Use a radiator key to open the bleed valve slightly (at the top side of the radiator). You’ll hear a hiss as the air escapes — once water starts trickling out, close it again.

🔧 If you're unsure how to do this safely, give us a call — we’re always happy to help.

2. Sludge or Debris in the System

Symptom: Radiators are cold at the bottom or have patchy heating.

This usually means there's a build-up of sludge — a mix of rust, dirt, and limescale — in your heating system. It settles at the bottom of radiators and stops the hot water from flowing properly.

🛠️ Solution:
A power flush or chemical flush can remove sludge from your system. It's a job best left to a qualified professional, but it can drastically improve your heating efficiency.

3. Radiator Valves Not Working Properly

Symptom: Some radiators stay cold while others heat normally.

Thermostatic radiator valves (TRVs) or manual valves can sometimes get stuck, especially if they haven’t been adjusted in a while. If the valve pin is jammed, hot water won’t be able to enter the radiator.

🛠️ Solution:
Try turning the valve fully on and off. If it still doesn’t work, the pin may be stuck — gently pressing it can free it up, but be careful. If the valve is faulty, we can replace it for you.

4. Incorrect Balancing of Radiators

Symptom: Radiators furthest from the boiler don’t heat well, while those nearest get very hot.

This is often caused by an unbalanced system. If water is flowing too freely to some radiators and not enough to others, you’ll get uneven heating across your home.

🛠️ Solution:
Balancing radiators involves adjusting the lockshield valve on each one to control how much hot water flows through. It can take a bit of time and trial and error — something we’re happy to help with if you’d rather not tackle it yourself.

5. Boiler Pressure Too Low

Symptom: Multiple radiators not heating, or heating very slowly.

Low boiler pressure can affect how well your heating system works. Most boilers operate best at around 1.0 to 1.5 bar when cold. If the pressure is too low, hot water may not circulate efficiently.

🛠️ Solution:
Check the pressure gauge on your boiler and top up using the filling loop if needed. If the pressure keeps dropping, you may have a leak that needs investigating.

6. Old or Poorly Sized Radiators

Symptom: Radiators take forever to heat or don’t heat rooms effectively.

In older properties across Edinburgh, we often find radiators that are outdated or simply too small for the room they’re in. Even if your system is working perfectly, they may not be delivering enough heat.

🛠️ Solution:
Consider upgrading to more modern, efficient radiators — or adding an extra one to particularly cold rooms. We can advise on the best size and placement for maximum comfort.

Final Thoughts: Don’t Settle for a Cold Home

Radiators not heating properly can be more than just an inconvenience — they can mean your system is working harder than it needs to, costing you money and putting unnecessary strain on your boiler.

Most issues are relatively easy to fix with the right tools and knowledge, but if you’re unsure, it’s always best to speak to a professional. At Able Girl Plumbing, we offer friendly, no-fuss help to get your home heating running smoothly again.