If one or more of your radiators are cold at the top and warm at the bottom when you have your central heating on, it could be that there is air or gas trapped inside. This greatly reduces the radiator’s effectiveness and could mean you’re spending more money than you need to by having your heating on more often.¯¨
Thankfully, there is a simple process to fix the problem – bleeding the radiator, so here’s a step-by-step guide:
1) Establish which radiators need bleeding
Turn your heating on so all your radiators come on and check if any have cold spots. If a radiator does have cold spots, it’s likely it will need bleeding.
2) Allow the radiators to cool
Once you’ve established which (if any) radiators need bleeding, turn your heating off again so they can cool down. This also prevents any additional air from entering the system.
3) Cover the nearby area
It is wise to have a bowl next to any radiator you are going to bleed to catch any water that may leak during the process.
4) Bleed the radiators
For most radiators you will need a radiator key in order to bleed them. If you don’t have one, you may be able to use a flat blade screwdriver or get a replacement key at a DIY store. You then need to find the bleed valve. This is usually located at the top of the radiator at one end.
Hold the key or screwdriver with a cloth as any water that escapes could be very hot. Turn anti-clockwise about half a turn. If there is any air or gas escaping, you will hear a hissing sound. When all the air has gone, water will start to come out and you should re-tighten the valve to its original position again.
5) Check the radiators
Turn the heating back on and after a couple of hours, check any radiators you bled to see if the temperature is now the same all over. If the problem persists, you may need to check the pressure on your boiler or have an engineer take a look.