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How to bleed a radiator


The 21st of December is when Winter officially begins it feels like it has come a lot earlier than that.

Are your radiators ready for the cold months?

During the summer, domestic and commercial properties heating system commonly sit idle with little thought being given to them. Which most likely means that it has been a long long time since the radiators in the building have been bled.

To help you get back into the practice of bleeding a radiator, here are our step by step guide to bleeding a radiator. Bleeding a radiator is important to ensure that there is no air in the system for greater energy efficiency of the properties radiators.

Warning: The water inside of a radiator can be very hot.  Please take care when bleeding a radiator so that you do not scold yourself.

How to bleed your radiator

1. Ensure that the radiators in the property are evenly warmed up.  Depending on the size of the property and how many radiators are fitted, this may take a while.

2. Going from radiator to radiator, check each one to ensure that there is an even temperature spread across the whole area of the radiator.  If there is not an even heat spread (ie. the top of the radiator is cold and the bottom is hot) then that radiator has air in it and needs to be bled.

3. Turn off the boiler system and wait for the radiators to cool.

4. On the first radiator, using what is called a radiator bleed valve key, open up the bleed valve that is generally located in the top corner of the radiator. Turn the bleed valve anti clockwise slowly. Have a cloth or rag to hand and position underneath ready to catch any excess liquid from the radiator.  As the valve opens, it should emit a hissing sound as air escapes from the radiator.

5. Once the hissing sound stops, water inside of the radiator will begin to leak out.  At this point, close the bleed valve by turning the radiator key clockwise.

Repeat steps 4 and 5 for all of the other radiators in the property.

6. When you bleed radiators, it can lower the boiler pressure.  If the boiler pressure has dropped below 1 bar of pressure then you will need to re-pressurise the system (It should be between 1 and 2 bars of pressure).


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