How to Bleed Your Radiators

Do Your Radiators Require Bleeding?

To identify if your radiators have trapped air and required bleeding:

  • Turn on your boiler / central heating system.
  • Turn up the temperature on your controls
  • Ensure that all radiators valves are fully open (turn anti-clockwise)
  • Check that each radiator in your house is getting warm, taking care not to burn yourself

If you discover that some of your radiators have a cold spot, or are hot at the bottom and cold at the top, the chances are, your central heating system has air trapped inside it, and your radiators require bleeding.

this is an easy and simple job, that you can execute yourself by following the guide below:


Bleeding Your Radiators in 7 Easy Steps

1 Ensure your boiler and central heating system is switched off
To make sure that no more air enters your system whilst bleeding your radiators, you will need to switch off your boiler / central heating sytem.

2. Locating your radiator bleed valves
The older type bleed nipple is usually a square bit inside a round hole, located at the top on one side of your radiator, this type of bleed nipple will require a bleed key to open.  Some modern radiators are slightly different and can be opened using a small flat headed screwdriver.  Please see examples below:

Old Type Bleed Valve
Old Type Bleed Valve
New Radiator Bleed Valve
New Radiator Bleed Valve

3. Obtaining a radiator bleed key
If you don’t already possess a radiator key, you can purchase one from most DIY stores for a couple of pounds.  They look like this:

Radiator Key
Radiator Key

4. Protect your carpet and decor
Place a dust sheet or towel on the floor under the bleed valve.  Have a dish cloth to hand to hold by the bleed valve.

5. Time to bleed the trapped air from your radiator
Holding your cloth in one hand, turn the radiator bleed valve anti clockwise about 1/4 of a turn using your radiator key / flat head screwdriver.  You should hear a hissing sound as the air escapes the valve.

6. Tighten the bleed valve back up
Once all the air is removed it will be replaced by water (this is where your cloth comes in handy!).  At this point, tighten the bleed valve back up by turning clockwise.

7. Switch your boiler and central heating back on
Leave it on for a couple of hours, then revisit each radiator in your home and check that you have a nice, even temperature with no cold spots.