5 easy step: how to easily bleed a radiator

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Radiator bleeding

The radiator is used to heat the room on winter or cold days. But sometimes even when all the radiator is on, some of them will feel cold on top and warm at the bottom. This is not the indication of a spoiled radiator but simply air is trapped inside. To solve this problem, you need to do radiator bleeding.

The common signs

Sometimes we have no idea why the radiator is not warm enough and decide to call the plumbers or professionals. Bleeding is a very simple process and can be done by yourself. But before you can decide if bleeding is needed you need to know the common signs of it. Turn the central heating on and check for these signs:

  • The top of the radiator is cold
  • Mildew or cold patches on the wall
  • Strange gurgling or rattling sound

Tools needed

Before starting the bleeding process, you need to make sure you have all the tools needed. The following are the common tools needed before you start bleeding:

  • Work gloves
  • Radiator key
  • Plastic tub or bucket
  • Cleaning clothes

The steps

Steps 1 – Determine and check

The first step would be to determine which radiator needs bleeding. Put your central heating on high and check to see if any of the above sign listed occurs. Once you determine which radiator needs bleeding immediately turn off the central heating. This is done to prevent further air to get into your radiator. But before you do anything else please check the lock shield and thermostatic valve. Sometimes one of these could lead to a cold radiator. If there is no problem with this, then you can proceed to do the bleeding.

Step 2 – open the valve

The valve will be on the top edge of the radiator. For this, you will need your radiator key. By using this key, turn the valve in anti-clockwise. Did you lose your radiator key? We will teach you how to bleed radiators without a key. Based on your valve design you can use a normal screwdriver if it is a slotted bleed screw. If it has a hexagonal or square design then you can use players or Allen keys to turn it anti-clockwise. You only need to open the valve just enough for the air to come out.

Step 3 – Close the valve

Once the valve is opened the air will start to come out making a hissing sound. Once all air has come out, a water gurgling sound can be heard and at this moment you need to immediately close the valve by turning it clockwise. At the same time put the towel below the radiator to catch the excess or leaking water.

Step 4 – Boiler pressure

This is a very important step because once the water starts to come out the boiler pressure might drop. Make sure there is 2 bar when on and 1 to 1.5 when off. If too low then it needs to be repressurized. After all is done, check again to see the pressure level. If it is in green reading then you can proceed to the next step and if it is in yellow, it still needs to be pressurized. 

Step 5 – Heat test

Once all is done, turn the central heating on and check for any abnormal signs. If there are no abnormal signs then your whole process is successful and you can enjoy back the heat needed on a cold night.


The bleeding process is very simple. You do not need a plumber to do this and can do it yourself. Just follow these simple steps and save your money and time.

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