‘Bleeding radiators’ is when you let out any air that has become trapped inside.
Trapped air or gas prevents hot water from heating your radiator fully. The good news is, bleeding radiators is a simple job that you can do yourself, and it can make a real difference to how energy-efficient the heating in your home is.
While this isn’t a hard thing to do, please follow these instructions with caution. If you don’t feel confident about what you’re doing, stop and get advice from a qualified heating engineer.
Step 1: Turn your heating on and get your radiators hot
Turn on the heating so that all radiators in your home come on - you may need to turn up the temperature on your thermostat and individual radiator temperature controls to make sure they all come on.
Step 2: Find out which radiators need bleeding
Once your radiators are all hot, go and check each one individually to see if all parts of the radiator are warming up. Be careful - radiators can get very hot and you don’t want to burn yourself.
Cool spots, particularly towards the top of the radiator, mean that there could be air or gas trapped and therefore you'll need to bleed that radiator.
Air or gas is more likely to get trapped in the highest radiator in the home. It can also sometimes get trapped in the coil that runs through the hot water cylinder, as that can often be the highest point in the system.
Step 3: Bleed the radiators
Before you bleed any radiators make sure your central heating is switched off.
Bleeding radiators usually requires a radiator key, but with more modern radiators you can use a flat-blade screwdriver.
At the top of the radiator at one end there will be a valve. You can attach the radiator key to the square bit in the centre or put the end of the screwdriver into the groove.
Hold the key or screwdriver with a cloth, and have another cloth ready to catch any drips, then slowly turn the radiator key or screwdriver anti-clockwise – if gas is escaping you’ll hear a hissing sound.
Once there is no more gas, liquid will come out and the valve will need to be closed quickly. With the more modern screwdriver operated escape valve, liquid is likely to emerge as a jet rather than a dribble.
Step 4: Check the pressure
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.
Afterwards, you may want to run another ‘hot test’ to check that your efforts have been successful.
That’s it! Congratulations, now you know just how simple bleeding radiators can be!