Is your boiler on but your radiator just doesn’t seem to heat up? Is your radiator warm at the bottom but cold to the touch in the top section?  

Problems such as these may be a strong indication that your radiator is in need of bleeding to get the heating system working again. Don’t worry however, bleeding your radiator is generally a quick and straightforward process that will get your home feeling warm and toasty again in no time.  

• What Does Bleeding a Radiator Mean?
• Why Should I Bleed My Radiator?
• What Will I Need?
• How Do I Bleed My Radiator
• How Often Should I Bleed My Radiator?

Put quite simply, bleeding a radiator means releasing air that has been trapped inside your heating system. When air becomes trapped inside your radiator it can rise to the top, taking up the space where hot water should be and causing cold spots. This prevents your radiator from heating the room effectively.

Aside from cold spots, another prominent indicator of trapped air is the sound of flowing and gurgling coming from your radiator or banging noises in your pipes. It’s also a more common problem in un-vented heating systems.  

Not only does trapped air in your radiator stop the system from warming your home, but it also can cause a significant rise in energy bills.  

Your radiator coordinates with your boiler to produce heat. This means that even if you aren’t feeling the warmth in your home, you are still paying for the same amount of energy as if you were.  

Bleeding your radiators also helps to enhance the energy efficiency of your living space, perfect for those who want to lead a more environmentally friendly home.  

• Radiator bleed key or flat-head screwdriver (dependent on your radiator style) 
• Cloth  
• Old towels 
• Container  
• Protective gloves  

Step One – Turn on The Heating 

The first step to bleeding your radiator is turning on your central heating so that your radiator can warm up fully. You should allow all of the radiators in your home to reach a completely heated state before moving on to the next step. 

Step Two – Check Your Radiators 

The next stage is checking all of the radiators. Walk around your home and check each radiator for signs of trapped air, singling out each one that needs bleeding. Remember, the main signs of trapped air are: 

• Feeling cold spots anywhere on the radiator 
• Hearing gurgling, clucking or banging sounds
• Feeling that the top section is much cooler than the bottom 
• Noticing that the radiator is taking a significantly longer time to warm up 

Ensure you are staying safe whilst touching the warm radiators to avoid burning yourself. It may be a good idea to wear some form of protective gloves to keep your hands safe just in case. 

Step Three – Turn Off the Heating 

It is highly important to remember that before bleeding your radiators, you switch off your central heating once again. This is because some water pumps can suck even more air into the system if they are turned on during bleeding.   

You also run the risk of burning yourself and damaging the floor with hot water so keep your radiator intake valves open but ensure the heating is turned off before the next step.   

Step Four – Cooling Down 

Before progressing further, wait for your radiators to fully cool down. Keep checking over all sections of the radiator to make sure that they are cooling down and don’t start bleeding if you still feel warmth.  

This is vital as boiling water may jet outwards when you open the valve plus the bleeding may not be as effective if you don’t let the radiators settle first.  

Step Five – Preparation  

Now is the time to grab your supplies and prepare the area around your first radiator for bleeding. Put the old towels down around the radiator to completely cover your flooring, ensuring it is fully protected from any leakages that may occur. Make sure you have your bleed key, cloth and container well within reach.   

Bleed valve keys are usually supplied with the radiator, although you can easily order or buy another at a DIY store if yours is misplaced. Some modern radiator designs sometimes even allow the use of a flat-headed screwdriver.  

Step Six – Locate the Bleed Valve 

The next step is locating the bleed valve on your radiator. This is typically located at the top of the radiator and looks like a round hole with a square inside of it. The bleed valve is where all of the trapped air and water will be released so make sure the space underneath is completely covered with the old towels and that your container is placed underneath. 

Step Seven – Open the Bleed Valve 

Now it is time to loosen the bleed screw and release the trapped air and water. Carefully insert your radiator key or screwdriver into the square part of the valve and you should notice that they lock together.   

Slowly turn the bleed valve anti-clockwise, using the cloth to maintain grip and catch any initial drips. A quarter to half turn is sufficient – make sure you never open the bleed valve completely.   

At this stage, you should hear a hissing sound as the air begins to release from the radiator. Wait for the hissing to stop entirely, at which point the water trickling out can be easily mopped up and dripped into the container.   

If you are using a flat-head screwdriver on a more modern radiator design, don’t be worried if the water releases in more of a jet stream than a dribble.   

Step Eight – Water Stream 

Continue bleeding the radiator until no more air is being released, only water. You will know at this point that the bleeding process is complete.  

Dependant on the style and size of your radiator, the bleeding can take varying lengths of time – usually around 20 to 30 seconds, although bigger radiators can take up to a minute.  

Step Nine – Re-tighten the Bleed Valve 

Next, use the radiator bleed key or screwdriver to re-tighten the bleed valve, rotating in a clockwise direction. Again, rotate the screw carefully, ensuring you don’t overtighten as this can cause damage to your radiator. Use an old towel to remove any excess water that has leaked onto the radiator surface or pipes to prevent rusting.  

Step Ten – Repeat 

Now you have successfully bled your first radiator, it is time to repeat the process with the other radiators in your home. Ensure you follow all of the steps each time to ensure the best results.  
It is advised that you begin on the ground floor and work your way upwards as air rises through the heating system.  

Step Eleven – Turn the Heating On – Again...

Once all of your radiators are bled, you need to switch the central heating back on to check that all radiators are working. Walk around your home, touching each section of the radiators to ensure that they feel warm all over with no gurgling, cold spots or long heating times.   

Also, check that there are no leakages or drips coming from the bleed valve. If you find that a radiator is still showing signs of trapped air, then it may be necessary to try bleeding them again.   

Step Twelve – Heating Pressure Level 

It is also key to check that your boiler is showing its advised level of water pressure in the green zone which is usually around 1-1.5 bar.   

During the process of releasing air from your radiators, the overall pressure of the heating system will have been lowered which may mean heat may not reach the upper floor radiators if it has fallen too low.   

If you find that the pressure has indeed fallen below the recommended level, you will need to re-pressurise the system. Locate the central filling loop on your boiler – this usually looks like a tap or lever and is joined to your main water supply.   

Turn the tap to adjust the pressure to the correct level. If you find you have re-added too much pressure into the red zone, you will also see there is a bleed tap to help reverse this.   

There is no set timeframe in which you should regularly bleed your radiators, however, you should always be keeping an eye out for any of the signs discussed previously. If you are finding that your radiators need bleeding very regularly, then it may be best to consult a professional just to make sure there aren’t any further problems with your heating system that you are unaware of.