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How to bleed a radiator in a central heating system

Here is a simple guide from a heating engineer on how to bleed a radiator in a central heating system.

Example… you turn your heating on sit on the sofa and watch TV. After a while you think why the room is not warming up so you touch the radiator and it’s not hot! Don’t panic, the first thing you need to check before calling a plumber is to check if the radiator is actually on. You may think 'why would it be turned off?' Do you have children? You get the point. If you have a (TRV), it’s easy to turn off simply turn anti-clockwise for on and clockwise for off easy as that! Wait a while and see if that resolves your issue.

Still cold? It could be air locked in the radiator or the pipework to the radiator. Again an easy fix and I will take you through it step by step. Check any visible pipework you can and see if it’s hot if yes go to the radiator, is the radiator only hot half way up? If so chances are you need to remove the air and this will resolve your problem.

How to remove air from a radiator

  1. Firstly do you have a radiator bleed key? If you do go to step 2. If not any local hardware shop will sell one.
  2. Now you need to turn off your central heating to stop yourself getting burned. And to prevent any components running dry and causing faults.
  3. Get yourself an OLD cloth or some kitchen roll this is to catch the water that comes out of the radiator it’s usually black so we don’t want your carpet being stained!
  4. So down to business, firstly you need to find the bleed valve on the radiator, usually on the side sometimes they will be on the back so keep an eye out.
  5. So you have located the bleed valve. Now grab your bleed key and simply turn the bleed valve anticlockwise slightly, only a little and defiantly not all the way out! If you take it out water will fly out at 2 or 3 bar and you’ll be battling to get the valve back in, trust me I’ve seen it happen. Also your carpet will definitely be stained. So be sure to only slightly open it, you will know when it’s open enough because you will hear a hissing sound. This sound is the air being removed from your radiator and being replaced with water.
  6. The hissing will slow down and you will start to get water bubbles coming out, this is an indication the radiator is almost full so get your tissue at the ready.
  7. Once water starts coming out, simply shut the valve by turning clockwise with your bleed key.
  8. Well done, you have just bled your radiator!
  9. Now you may need to consider how to add pressure to your boiler if it is of the pressurized type. To find out, go to your boiler and you will see a gauge with green and red and 1-4 in this should be in the green or just over 1. Numbers represent ‘bar’. If you can’t see one chances are you don’t have a pressurized system.
  10. There you have it, fairly easy right? Well done you have saved yourself a call-out charge!

I hope this has helped you resolve your issue, if not call us on 07412 78734