How to Bleed Your Radiators

Do you want to know how to bleed your radiators? Have you wondered why you need to bleed them? Read on to find out more and learn how to bleed your radiators at home. Trapped air in your radiators causes cold spots and reduces the efficiency meaning a colder home and more expensive heating bills. ‘Bleeding’ your radiators is letting out the trapped air which has become caught inside, so they can work at optimum efficiency again.

The perfect time to bleed your radiators is when your central heating isn’t warming your home as it should. It doesn’t matter about a certain time of the year although I’m sure you’ll agree you want maximum efficiency for those cold winter evenings.

Bleeding your radiators is something you can do easily at home by following our step by step instructions but first you need to do the following:

Turn on the heating so that all radiators throughout your home turn on.
Once your radiators are nice and hot, check each one individually to see if all parts of the radiator are warming up equally.  Radiators can get very hot, so please be careful – you don’t want to burn yourself! You’re feeling for any cool spots, particularly toward the top of the radiator as this means that there could be air or gas trapped and you’ll need to bleed that radiator.

It is very important to check for signs of a more serious problem before you start the radiator bleeding process. Predominantly check for rust or water underneath or on the radiator as this could be the sign of leaks in your heating system. Also check that your boiler power light is on (or the pilot light is lit), the boiler pressure is at the right level, and that your boiler isn’t leaking.

It’s time to switch off your central heating as this will allow you to complete the project without burning yourself or soaking the floor or inadvertently sucking more air into the system.

It is also a good idea to lay old towels on the floor around the drain plug and capture any spillage with an old jug or pot. Remember that old radiator water can be quite dirty and discoloured so if you have a light coloured carpet you don’t want to risk the possibility of any spillage!

The radiator you bleed first is completely dependent on the layout of your home and position of your boiler. If you live in a 2 story house with the boiler upstairs, you would start with the downstairs radiators first as they’re furthest away from the boiler, if the boiler is downstairs start with your upstairs radiator.

Firstly, you will need a radiator key. These are available at hardware stores or if you can’t find one you can use a flat-blade screwdriver. You will also need some old cloths or kitchen roll.

At the top of your radiators 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, and place the bowl or tray directly underneath it at the base of the radiator.

Fit the radiator key over the bleed screw tightly, cover it with another cloth and slowly turn the key anti-clockwise for about half a turn. As the air releases, you’ll hear a hissing sound. At this point, hold the cloth close to prevent water dripping or spitting. It is important that you do not remove the bleed screw!

After air stops hissing and water begins to trickle out steadily, tighten the screw again quickly, being careful not to over-tighten and damage the valve.

Repeat this across all of your home’s radiators.

Now you need to check the pressure by having a look at the gauge on your boiler. If the pressure is too low, you’ll need to top it back up again using the filling loop on your boiler which is usually a lever or tap on the main water supply.

Finally, test to check if your efforts have been successful by turning your heating on again and waiting for all the radiators to heat up and see if there are any cool spots. If there are, some of your radiators may require a second bleeding. If the problem is still not solved – contact a qualified heating engineer.

If there are no other obvious concerns, your home’s heating will almost certainly benefit from radiator bleeding.

Still unsure you can bleed your radiators yourself? Let Complheat help you out!
We can also provide follow-up advice on care and maintenance, and perform annual servicing to ensure your heating system remains in prime condition.