How to Bleed a Radiator

Radiators can sometimes feel cold in places despite the heating being on, or can make gurgling noises. If this sounds familiar, then it is time to bleed your radiators.

Small bubbles of air can circulate in the water of your central heating system. This is common and nothing of concern. But when the air bubbles all accumulate in your radiators, it can lead to them being less effective. Bleeding a radiator releases the trapped air.

Bleeding radiators is a simple job, and we have all the advice and guidance you need below. You want your central heating to be working in tip-top condition over winter and the colder months, and releasing the air helps the water to circulate efficiently.

Still have areas of cold in your home? Whether it is a spare room with no radiators, or you just need a boost while you're bleeding the heating system, you can hire heating from Speedy Hire which can offer temporary warmth.

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How to bleed a radiator

You will need:

• Radiator bleeding key
• Cloths
• Jug or other collector (such as a mug or jar)

Method

1. Turn off the heating

Ensure all radiators are turned off, and that your central heating is off too and won't come on until the job is done. Wait for warm radiators to cool down before beginning the job.

2. Locate the radiator bleed valve

A radiator bleed valve is usually small and rounded in shape, with a square central piece which the key fits over. They are often at the top edge or corner of your radiators. This is what you will turn to release air.

Place the jug or mug underneath this on the floor, which will catch any water.

3. Open the valve

Use the key to turn the bleed valve slightly anti-clockwise. You may hear a hiss or whistle sound, which is the air escaping. Don't turn the valve too much, but you want to be able to hear this.

4. Close the valve

When the hissing stops, water may start to drip out of the valve instead. This is why you must wait until the radiators are cool. Turn the key to the right again to close the valve once this starts. The mug or jug below the valve should catch any water. Use a cloth to wipe any drips.

5. Check other radiators

Now you know what to do, you should check all of the other radiators just in case. There is a good chance they also have trapped air inside.

A good rule of thumb is to bleed downstairs radiators first, starting with the one furthest away from the boiler. Then move upstairs.

6. Check your boiler pressure

Releasing that trapped air may have caused your boiler pressure to dip. If so, top it up until the needle is in the safe zone. This is usually marked in the green colour on the pressure gauge, or around '2'.

FAQs

When should I bleed my radiators?

It is a good idea to bleed radiators before winter, when your central heating will be used the most. This will ensure it is effective from the off. But radiator bleeding can be done any time you feel your heat isn't quite working to its optimum levels, or radiators feel cold or are noisy.

Radiators should be bled at least once per year.

Bleeding my radiator didn't solve the cold spots - what do I do?

Bleeding radiators should help reduce cold spots and noise. If not, it could be a sign there is an issue with either your radiator or heating system.

Your radiator may be rusting inside, or dirt may have built up in your heating system. There may also be a leak in your system. Check your boiler, pipework, and radiators for any obvious signs of a leak, such as damp floors or regular dips in boiler pressure.

If all seems fine, your heating system may need flushing to release and clear our dirt trapped inside it.