Bleeding a radiator is an efficient way to get rid of cold spots. The process enables you to remove air, vent or purge a radiator and it is done by opening the air vent at the top of the radiator. 


Here our expert, Jason, provides a step by step guide to the easiest and most effective way to bleed a radiator.


For more information, visit www.featureradiators.co.uk.

How to Bleed a Radiator

To ensure effective performance of a water-filled radiator, you need to make sure that the radiator has been "bled" properly.  Bleeding a radiator means getting rid of any air that has accumulated at the top of radiator. When air is present, there is no water, which means no heat. Bleeding a radiator is done by opening an “air vent” otherwise known as a “bleed valve”.  Ideally radiators should be checked for air accumulation at least once a year.

To bleed a radiator you will usually require an appropriate tool, namely a flat headed screwdriver, a “bleed key” or a spanner.  Bleed keys (vent keys) are not included as standard but can be purchased from a plumbers' merchant or home improvement store. 

Bleeding a radiator is a simple process:

1.    Ensure both valves at the bottom of the radiator are open;

2.    Get a bleed key (vent key), screwdriver or spanner ready to open the bleed valve (air vent) at the top of the radiator.  Have a rag or cloth ready to catch minor drips;

3.    Use the tool to open the air vent and release the air holding the cloth underneath;

4.    Listen for the change in sound; you will hear a hissing noise at first, which is the sound of air escaping.  Vent the radiator until the sound changes and you get a steady stream of water.  At this point you can retighten the air vent using the tool.

5.    Once you have bled the radiator, turn the heating back on and leave the system to flow for half an hour.

Please note: On first filling a system, it is air that is vented from a radiator. However, from then on the periodic venting required is actually releasing hydrogen that is the by-product of rusting in the system.  If regular bleeding is continually required, then this is a strong indication that the system requires draining, cleaning and refilling incorporating a corrosion inhibitor to prevent further rust in accordance with BS5449 section five commissioning.  Alternatively, if regular bleeding is required then this could indicate a leak that is letting air enter the system.

Alternatively modern radiators do sometimes come with “automatic bleed vents” which release air from a radiator whenever necessary, meaning that you do not need to bleed the radiator manually.  These are great for convenience, however there are instances of automatic bleed vents causing damage to a radiator as regular venting can mean regular water seepage which can lead to corrosion.    

For more advice on maintaining your radiators, contact a radiator specialist such as Feature Radiators; their expert team can provide technical help on a variety of radiator related subjects.  Contact them on 01274 567789, view their website http://www.featureradiators.co.uk or visit them in person at their showroom at The Old Post Office, 134-140 Main Street, Bingley, West Yorkshire. BD16 2HL

My radiator isn’t as hot as it should be, why?

A cold radiator or a radiator with cold spots often indicates that the water is not flowing through the radiator as it should. This is almost always down to an installation issue and is very rarely due to a problem with the radiator itself.

This means that the issue should be easy to correct by following the step-by-step instructions detailed below.

1. Bleed the radiator

Firstly, you need to make sure the radiator has been “bled” properly. Bleeding a radiator means getting rid of any air that has accumulated at the top of radiator, using an air vent/bleed valve. Where air is present, there is no water, which means no heat.

Ideally radiators should be checked for air accumulation at least once a year. Bleed keys (vent keys) can be purchased from a plumbers’ merchant or home improvement store.

Bleeding a radiator is a simple process:

a) Ensure both valves at the bottom of the radiator are open;
b) Attach the bleed key (vent key) onto the bleed valve (air vent) at the top of the radiator;
c) Unscrew the air vent and have a cloth ready to catch minor drips;
d) Listen for the change in sound; you will hear a hissing noise at first (the sound of air escaping), then it will change to a steady squirt of water. At this point you can retighten the air vent.

Please note: On first filling a system it is air that is vented from a radiator. From then on the periodic venting required is actually releasing hydrogen that is the by-product of rusting in the system. If regular bleeding is continually required, then this is a strong indication that the system requires draining, cleaning and refilling incorporating a corrosion inhibitor to prevent further rust in accordance with BS5449 section five commissioning.

2. Check that the valves are open

Make sure the valve is fully open, to ensure water can flow into the radiator.

3. Is a “flow diverter” required?

Certain radiators need “flow diverters” that are fitted internally, to ensure that the water flows in the right direction around the radiator. A flow diverter is designed to ensure that all parts of the radiator get as hot as they should. If a flow diverter is required then it will be sent out with your radiator but occasionally installers do forget to put these in. Failure to install a flow diverter when it is required will almost always result in a radiator not performing properly.

4. Does your system need ‘balancing’?

Finally, if your radiator is still not hot all over, then you need to check whether your radiators need ‘balancing’. Your plumber or heating engineer should balance your system following installation or maintenance of your central heating system. Balancing is adjusting the flow of water through each radiator on a system so that all radiators are running at equal temperatures and take an equal amount of time to reach their operating temperature. Lack of balancing within a system is often the cause of cold spots on radiators, radiators failing to heat up properly, or radiators making noises. If your radiator is not heating up correctly then it is highly unlikely that the problem is caused by a manufacturing fault.

Please note: If you have paid a plumber or heating engineer to install your radiator(s), then unless there is a manufacturing fault with the radiator(s) (which is rare), then any newly installed radiators should function correctly before that person leaves your property. Your installer should also ensure that the performance of any existing radiators on the system has not deteriorated as a result of the work carried out. Problems are sometimes caused by installers failing to balance a system following maintenance but these checks should be included as standard as part of the service provided by them.

For more information on radiators including expertise and technical advice from a specialist, then contact Feature Radiators on 01274 567789, meet the team at their showroom in West Yorkshire or visit http://www.featureradiators.co.uk/