How To Bleed a Radiator

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How to Bleed a Radiator


Boiler Installation Kent



We all know that feeling. Its been a long day at work. You sit back to watch that film you’ve been dying to see. It’s not as cosy as it should be because you’re chilly. You get up to feel the radiator and it’s cold. Well not completely, the bottom of it is lukewarm. What do you do?


When was the last time you bled your radiators? Did you say ‘never’ as you don’t know how? It’s not as hard as you think. The radiator has trapped air in it, that’s all and it’s quite simple to release that air.


Boiler Installation Kent have written some step by step instructions on how to bleed your radiators. It might be a good idea to print this page and keep it somewhere handy for next time.    


Turn the Heating Off


First things first, make sure the central heating is turned off. If you don’t, when you open the valve there’s a chance that air could get sucked back into the radiator.


Radiator Key


The next thing you need is a bleed key and a piece of tissue or cloth. The bleed (radiator) key should have come with the radiators, but if you have misplaced it, you can buy one from most DIY stores. Some modern radiators don’t need a radiator key and can be opened with a screw driver.


Bleed Valve


It shouldn’t be hard finding the bleed valve. This is usually on the top right hand side of the radiator.


Protect Yourself


The water is very hot so protect yourself. Use a cloth to turn the key in the same manner you would use oven gloves.


Bleeding the Radiator


  • Hold the tissue, cloth or a small bowl under the valve to catch the excess water.
  • Use your key to turn the valve anticlockwise.
  • You shouldn’t need to turn it more than half way.
  • You will hear a hissing sound as the air begins to escape.
  • All the air will be pushed out because the fluid is under pressure.
  • As soon as the water starts to escape, close the valve tightly.
  • When you have done one radiator the rest of them will be easy. Move around the house to the next one until you have done them all.
  • Once you’ve bleed all the radiators, make sure you tighten up all the valves properly.
  • Turn the central heating back on.


NB: If the central system is still on and the bolt falls out, never put your finger in the hole to stop the water, as the fluid is under pressure and can be forced into your finger.


Relevant Information


Although Boiler Installation Kent strives to provide correct and accurate information throughout all their websites, it is only a general guide to help our customers. This is not professional advice and we accept no responsibilities for any DIY work carried out by unqualified engineers.


Some gas and electrical procedures are required by law to be carried out by a qualified engineer.


We accept no liability for the damage to any persons or properties, and recommend that no minor under the age 18 or inexperienced person attempt the advice set out here.


If you have any doubt at all please contact a professional company.



Boiler Installation Kent covers the whole area of Kent.





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