How to Bleed a Radiator?

Bleeding your radiators can help keep your home feeling warm, save you money on your bills and help you do your bit for the environment. Your radiators are just as important as your boiler, so if you are paying energy bills to heat up an inefficient system, you are not getting the full heat benefit for your money.

Does the top section of your Stelrad Radiator feel cool to touch, while the bottom of it is nice and warm? Does the entire radiator feel cold?  Do you hear gurgling noises as your Heating system is running? If so, then these cold spots indicate that air is trapped inside the radiator which has risen to the top, you need to release (or bleed) the air trapped in your radiator, so the radiators can heat effectively when in use. Don’t worry, this is a common problem which you can easily fix with a few simple tips.

If you’re bleeding your radiators, we recommend you bleed them all a minimum of at least once a year – each one in the home – you may be surprised how much air you can get out of radiators that seem OK.

Unfortunately, if you have numerous cold or lukewarm radiators in your house it’s probably a larger issue with the full heating system. You could contact a local plumber to see if your Boiler is malfunctioning or to see if you need to flush your heating system.

If the radiators on the Ground Floor are hot but other floors are cold, then this may be due to the heating system having circulation issues (pump) which might be struggling to move the hot water through the system. We recommend calling a professional to check your full system.

Step By Step Instructions For Bleeding Your Radiator

After diagnosing the issue with your radiator, follow these simple steps to bleed your radiator:

Step 1.

Turn your heating off so that the pump is not running.Turn off your heating system

Step 2.

Once identifying which radiators are affected, wait for the radiators to cool so hot water doesn’t harm you whilst bleeding your radiator.

Wait for the radiator to cool down

Step 3.

To be clean and tidy from spillages you might need a cloth and towels, as well as a radiator bleed key.Cleaning equipment

Step 4.

Starting with the ground floor radiators first.

Start with ground floor

Step 5.

Locate the bleed valve, which is usually at the top on one end, the ‘key’ should fit correctly over the square release nipple. Don’t turn anything yet. Make sure your work area is covered with towels and you have the clean cloth handy.Locating Bleed Valve

Step 6.

Carefully turn the bleed valve key (or if possible, a flathead screwdriver) anti-clockwise a quarter turn. Hold the dry cloth to the valve to soak up the water and try to protect the wall. You may hear a hissing sound until all the air escapes.Turn the valve to bleed

Note: If the whole bleed valve is turning at once, you will need to hold against the turning direction with a spanner as this will remove the vent plug and cause damage.

Step 7.

Once all the air has been released water will start to run out of the hole, wait for a steady stream of water without any spluttering before closing the valve in a clockwise direction.Bleed until water comes out

Step 8.

Make sure you clean up any spilt water, wiping down the radiator, so the radiator doesn’t rust.Clean the radiator

Step 9.

Once you have completed these steps for all radiators in your system, check that the pressure setting is correct on the system if you have a Combination boiler. Turn the heating back on and check all radiators for cold spots, leaks and drips around the bleed valve. You may need to bleed some radiators again once the water has run through the system.Turn the boiler back on

Step 10.

If you have a sealed pressurised system, check the manufacturers recommended pressure setting is correct. Normally 1.2 to 1.5 Bar). By bleeding your radiators, the overall pressure will have been lowered. If the pressure is too low, you may need to top up your boiler with water.

Bleeding a Radiator Q&As:

How do you bleed a radiator without a key?

Look for a flathead screwdriver or similar tool in the toolbox to allow you to turn the small slot on the valve. But we advise you to get a radiator bleed key – available from all DIY shops – Ideally we want you to be able to open the valve and shut it properly!

Can you bleed a radiator when the heating is on?

To avoid being scolded when water escapes from the radiator we advise you to switch off your central heating and let the system cool before you bleed the radiators.

Do you bleed the radiators when they’re hot or when they’re cold?

To avoid being scolded when water escape from the radiator we advise you to switch off your central heating and let the system cool before you bleed the radiators.

How long does it take to bleed a radiator?

This can vary, depending on the amount of air that needs to be released from the radiator, the size of your radiator and whether you have all your kit ready. Typically, it takes 30 – 60 seconds for a radiator to be bled of air, but don’t be surprised if it’s a few minutes for large radiators, especially on older systems.

How often should you bleed radiators?

At least once a year – ideally twice. And then after you have had any serious work undertaken or a radiator removed for decorating on the heating system – replacement boiler or replacement radiators for example. Anything that may have necessitated having your heating system drained down.

What order should you bleed your radiators in?

Although you drain each radiator as a separate entity on the system if your home has two  or more floors you should begin bleeding the downstairs radiators first. Once you’ve bled all the downstairs radiators you move on to the upstairs and so on. All the way to the highest point.

We don’t recommend that you bleed just one radiator – it may seem that one is cold more than the others, but you may be surprised how much air you manage to extract by bleeding ones that seem fine to the touch.

What is bleeding a radiator?

It’s the act of removing unwanted air from the heating system. Hopefully your heating system has the right chemicals in it to ensure that the inside of the system doesn’t suffer from rust – which is a black magnetite sludge in your heating system that can settle in awkward parts of your radiators and impede water circulation around the system. Air in the system can be a contributor to the inside of the system beginning to rust and that can lead to leaks and other issues. Air + Water + Metal = RUST!

What does ‘bleeding’ radiators do?

It takes the unwanted air out of the system and allows the space the air was taking up to fill with water. This will help to ensure that you have the best possible water circulation in your heating system and a more efficient system.


You still have items in your basket

Would you like to checkout?