How to bleed a radiator banner

How to Bleed a Radiator

December 21st 2023


Has your radiator been making strange sounds recently, especially during the heating-up stage? Have you noticed that the radiator is cooler in specific places, usually around the top?

Radiator bleeding is the process of letting trapped air escape from your home’s heating system, which will help improve performance, stop annoying sounds, and save you money on your heating bills.

If you think you need to bleed your radiator, or multiple radiators in your home, read our step-by-step guide below.

How to know if your radiator needs bleeding

There are a few tell-tale signs that a radiator in your home needs bleeding, starting with a general feeling that your home is not heating up the way it usually does. To figure out which radiator is the culprit you should:

  • Firstly, turn your heating on and wait for it to warm up.
  • Secondly, feel the radiators to see which ones are cold at the top but warm at the bottom.

Bleeding a Radiator: Step-By-Step Guide

First and foremost, you will need a radiator key or a flat screwdriver, depending on the type of bleed valve that your radiator has.

Step 1 – Turn off your heating system

To avoid any burns, make sure that your heating system is completely turned off when you begin.

Step 2 – Identify which radiators need bleeding

To identify which radiators need bleeding, check for cold spots near the top as it indicates trapped air and the need for bleeding.

Step 3 – Prepare the area

Locate the radiator’s bleed valve and place towels or a small bowl beneath it to catch any water that might drip out.

Step 4 – Insert and turn the radiator key/screwdriver

Insert the radiator key or flathead screwdriver into the bleed valve. Turn it anticlockwise around a quarter to half a full turn. You should hear a hissing sound as the air escapes.

Keep the key turned until water begins to trickle out, then close the valve quickly by turning the key or screwdriver back clockwise. Make sure you tighten the valve gently to ensure it is closed securely to prevent leaks.

Step 5 – Check your boiler pressure

Once you have ensured that the bleed valve is securely closed, check the pressure gauge on your boiler. If it is low you might need to repressurise the system according to your boiler’s instructions.

Step 6 – Turn the heating back on

Now it’s time to turn your heating back on and do a final check that your radiator is heating evenly.

Note: It’s a good idea to keep an eye on the area around the radiator to check for any leaks, if there are any then you may need to tighten the valve slightly or consider replacing it.

Bleeding Radiator FAQs

Below you’ll find answers to some frequently asked questions about bleeding radiators.

Why is it important to bleed a radiator?

After a while, air pockets form inside radiators that cause the hot water in your central heating system to stop circulating efficiently, it’s in these situations that a radiator needs “bleeding”.

It’s important to check your radiators and bleed them regularly if needed, as air pockets can put a strain on your boiler  and central heating system and end up costing you more money on heating bills in the long run.

Should I bleed my radiators with the heating on or off?

Your heating system should be turned fully off before bleeding your radiators, to prevent any potential burns from leaking water.

How often should I bleed my radiators?

A good rule of maintenance is that you should bleed your radiators every year before the weather starts to get cold, but you should always bleed your radiators whenever they start to make strange noises.

Why isn’t my radiator heating up again after bleeding?

Your radiator might not be heating up after bleeding it because of an issue with your thermostatic radiator valve. In this instance, you can try adjusting it yourself or performing a radiator power flush.

If you don’t feel comfortable performing these steps, we recommend contacting a registered plumber.

How do I know what type of bleed valve I have?

There are two types of bleed valves commonly found on radiators, a manual bleed valve and an automatic bleed valve. The manual variant is typically located at the top of the radiator and is square-shaped, whilst the automatic variant is equipped with a mechanism that automatically releases trapped air from the radiator.

If bleeding your radiator doesn’t fix any issues you are having with your heating system, book a service to find out what is going on with your boiler.

For more information on the maintenance of your heating system, please get in touch today.

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