How Does Air Get into Radiators?

When your radiators are working normally and efficiently, they will work quietly in the background without any issue. However, they will require maintenance every now and again, especially if you begin to hear strange noises or they aren’t working as well as they should. A common issue your radiators will experience is air getting into them, but what causes the air in radiators and is there a way to prevent this from happening? Here’s how and why air can become a problem.

Air in Radiator Causes

As they have no main openings themselves to allow air in, you may wonder how air can get into radiators in the first place. This is all due to water flowing in and out of them from your central heating system when being used, carrying air that can then get trapped. There can be a few ways air can enter the system, including:

  • A build-up of hydrogen, caused by sludge build-up over time
  • A leak somewhere in the system, letting air in
  • If your system has an open tank, such as with immersion heaters
  • The natural expansion and contraction of the radiator
  • The water pump being installed above the supply tank in older systems

Whilst there are a few ways air can enter the system, some more preventable than others, removing the air is something you can easily do in most situations. Being aware of the air in radiator causes is one thing, but how can you tell this has happened and what should you look out for?

Signs of Air in Radiators

You can’t see the air in the system once it has entered, but you may be able to hear that it’s present. If your designer radiators are making a gurgling or bubbling sound, this can indicate air bubbles within the system. This can commonly be heard when you first turn your heating on, and it begins to warm up. Any air will begin to accumulate in your radiators, rising to the top. As warm water is rushing into cold radiators, the natural contraction and expansion of the metal will make noises such as creaking, which is nothing to worry about and can’t be prevented. Any bubbling or gurgling, however, can be resolved.

Another simple way to tell if you have air in radiators is to touch the top of them with your hands. If they feel cold in areas even after the heating has been on for a while, this will indicate trapped air. The air itself will not heat as quickly as water, so you will be able to tell quite quickly if there is not an even spread of heat across the radiator.

How to Remove Air in Radiators

If you have identified air in radiators throughout your home, the best way to remove this is to bleed them. By bleeding your flat panel, double panel or column radiators, this will allow the air trapped inside to escape. This is usually all you will need to do to resolve the issue and is best to be done regularly to avoid a large build-up of air. You should ideally have a radiator valve key that will allow you to easily release the air, inserting this into the valve to loosen it. You should:

  1. Turn off your heating and allow this to cool before starting
  2. Have the radiator valve key to hand and also some tissue or cloth
  3. Insert the valve key into the valve, there should be an opening at one end of your radiator.
  4. Turn slightly to begin releasing air, you won’t need to fully open the valve
  5. Some water may expel whilst the air is escaping, so use a tissue or cloth to catch this
  6. Once the air has escaped, retighten the valve

You can find more information in our how to bleed a radiator article to help with this.

The Issue with Air in Radiators

If maintained regularly, air getting into radiators will not cause you too many problems. Having a routine of bleeding your radiators can ensure most of it will escape and not build-up. The biggest issue with air getting in is preventing your metal radiators from heating up properly. If the issue isn’t resolved or ignored over time, you may find you have to keep your radiators on for longer during the colder months. This is because they take much longer to heat up and won’t be working as efficiently as possible due to trapped air.

Overall, the air in radiators can lead to potentially higher energy bills, as your radiators are having to work much harder, and possibly more corrosion internally with your central heating system. Very rarely will the build-up of air in your radiators cause any major or potentially dangerous situation, however, if you are concerned about noises that aren’t resolved such as banging, you should call out an engineer to investigate.

How Does Air Get into Radiators Still When Bleeding Regularly?

If you have found that you are having to bleed your radiators more often to release air, this could indicate a bigger problem. Ideally, you shouldn’t have to do this more than a few times a year in your household, so if you are finding there are still issues with heating performance, this may indicate a leak or low pressure. Having regular boiler maintenance can discover any other issues with your system if air in the radiators is happening more than it should.

A lack of water pressure in the system can be one of the other air in radiator causes, and can happen when bleeding the radiator. Check the pressure gauge on the boiler and if it is low, then you will need to re-pressurise the boiler to resolve. A build-up of sludge or hydrogen over time in your heating system from corrosion can cause blockages too. Hydrogen is caused by rust within the system, something more common in older systems. This causes sludge to build up and causes the radiator to feel cold at the bottom, the opposite of a build-up of air. If when bleeding the radiator you notice discoloured water comes out too, this could indicate sludge is present.

How does air get into radiators? As detailed above, there are many different ways, but most can be resolved quickly and easily by bleeding the radiators. If you have any queries or want more information about our range of vertical radiators, towel rail radiators and other heating solutions, please get in touch.