How to  bleed a radiator

How to bleed a radiator

Didier, Technical manager, Cardiff

Guide written by:

Didier, Technical manager, Cardiff

8 guides

Bleeding your radiators makes them work more efficiently and helps to save you money. An essential part of central heating maintenance, flushing the air out of your heating circuit can lead to pressure loss in the boiler so you may have to rebalance your system. Read on to find out how to bleed your radiators.

Important features

  • Identifying radiators that need to be bled
  • Bleeding a radiator
Shop our central heating radiators

Bleeding a radiator for optimal heating performance

If you have central heating powered by a boiler you must maintain your radiators and check that they are working correctly on a regular basis. If you notice that one or more of your central heating radiators are not heating properly, the issue is not usually serious.

Air can enter the heating circuit which affects the performance of the radiator. This can lead to excessive energy consumption and a less efficient heating system. The solution is to bleed the radiator(s) in question in order to remove the air and allow them to operate at full power.


  1. Finding out whether your radiator needs to be bled
  2. Bleeding a hot water radiator

Required skills


You don’t need to be a heating engineer to bleed a radiator. The process is very simple, and only takes a few minutes; a simple twist of your bleed valve and the job's sorted!

Time required


About 10 to 15 min per radiator

Number of people required


1 person

Tools and equipment

  • Needle nose pliers (or the correct type of bleed key for your radiator);
  • A basin and some rags.

Personal Protective Equipment (PPE)


Please note that is a non-exhaustive list; make sure your PPE is suited to the task at hand. 

Explore the ManoMano catalog
Protective gloves

1. Identifying radiators that need to be bled


It is very easy to find out whether your radiators are heating to full power or if there is air in your heating circuit.

  • Put your hand on your radiators, always starting with the lower part (near the ground) and working slowly upwards. If there is a noticeable difference in temperature in the upper part, it is because your radiators are partly filled with air and not with hot water. As a result, they produce much less heat.
Explore the ManoMano catalog

2. How to bleed a radiator


The bleed valve is always located at the top of the radiator. Depending on the model, you may need a bleed key, but in most cases, needle-nose pliers will be sufficient.

  • Using a pair of protective gloves (to ensure you don't get burnt) place a basin directly below the valve.
  • Gently unscrew the bleed valve until you hear a hissing sound that indicates that the air is starting to escape. At that point, stop unscrewing.
  • After a while, all the air will be released from the radiator and the water will begin to flow. Let the water run for a few seconds and then close the valve.
  • Once this has been done, all the air will have been released from the hot water radiator.
  • Repeat the process on all the radiators in the circuit with this issue.

Removing the air from your radiators will reduce the pressure of your heating system. You will have to top up your system's water level once all radiators have been bled (see the operating guide for your boiler for instructions on how to do this and information about operating pressure).

A few hours later, check all your radiators again to make sure they are all heating properly, and that the valves are not leaking.

More information

For more information on heating and cooling your home, check out the following guides:Space heater buying guideElectric radiator buying guideOil-filled radiator buying guidePortable air conditioner buying guide

Explore the ManoMano catalog

Shop our central heating radiators

Guide written by:

Didier, Technical manager, Cardiff, 8 guides

Didier, Technical manager, Cardiff

I spent ten years working in maintenance services, first as a Technician and then as a Head Technician. For eight years, I have perfected the methods and management of subcontracting. Today, I continue my career while I work on technically versatile projects. DIY: I love it. I like having the right tools. Precise work fascinates me, I like working with wood and metal and I do not hesitate to make something myself if it doesn’t exist. In my daughter's room, for example, has a bed built into her desk. My family and neighbors don’t hesitate to ask me for advice or troubleshooting. My experience in home renovation combined with my knowledge of the various building trades allow me to advise on tool choice with pleasure.

The products related to this guide