Why Are Your Radiators Cold?

We’ve all been there, you come home from work on a cold, chilly day and expect to be greeted by a lovely, warm, cosy house – but it’s not. 

You feel the radiator in the hall… it’s cold! You check the thermostat, check the timer came on, yep no problem there. What’s going on?

Firstly is the radiator cold at the top or the bottom? If the top of your radiators are cold you are in luck, you should be able to fix it. You need to bleed the radiator.

Don’t worry bleeding a radiator is easy - follow our step by step guide and we’ll show you how.

How to bleed your radiator?

Step 1. Check the radiators

When the heating is on go around your home and ensure the thermostat is open on each radiator. Then identify which radiators are still cold.

Now turning your heating off. The water in the system will be very hot so allow some time for the radiators to cool before you move on to step 2.

Step 2 – Bleed the radiators

  • Which type of radiator you have? At one end of the radiator there will be a valve.  Do you need a radiator key or a flat-headed screwdriver? You can buy radiator keys from most hardware stores if you don’t have one.
  • Then grab yourself some tea-towels or cloths
  • Place the clothes around and under the radiator to protect the walls from any spraying water
  • Use the key/screwdriver to slowly undo the valve (turn anti-clockwise) – you should hear a hissing sound
  • Keep the valve open until all the air is out and the water starts flowing out
  • Close the valve

Step 3 – Check again

To be safe -check the pressure by having a look at the gauge on your boiler. If the pressure is too low, you’ll need to ‘top up’. You can do this using the lever or tap on your boiler, known as the filling loop.

If you’re still not sure run another ‘hot test’ to check all the other radiators are hot. If not step again at Step 1 with the cold radiator.

That’s it. Your done!

How do radiators work?

Why is my radiator full of air?

There could be any number of reasons why your radiators fill with air.

Starting at the boiler the central heating system runs all over your house. Through walls, under floors, in the loft. That means there are lots of places that air could get into the system. When the boiler is on that hot water will flow around the system warming up the radiators on the way.

Just like when you boil a kettle and see the steam rise, hot air rises in your radiator. So once your heating is on, any hot air goes to the top of the radiator and blocks the water.

No water = no heat.

Remember a hot radiator is a happy radiator!

How often should you bleed radiators?

You shouldn’t need to bleed your radiators more than once a year. We recommend carrying this out as the weather starts to get colder, ahead of the winter season. 

If, however, you are having to do it every few months, we suggest contacting your local plumber for advice as you may have a larger issue somewhere in the system.

Bleeding radiators should be a regular part of your ongoing maintenance to keep the central heating system working as efficiently as possible. It can also reduce you energy bills as you boiler won't be working quite so hard to warm you home.

To ensure your central heating is fully protected why not take a look at our central heating cover?