How to Bleed a Radiator: A Step-by-Step Guide

Butler & Rose Designer 3 Column Horizontal Radiator - Matt Anthracite -  600mm Tall

Bleeding a radiator is an essential maintenance task that helps ensure your heating system runs efficiently. Trapped air inside the radiator can cause uneven heating radiators uk or cold spots, which can make your home less comfortable and increase your heating bills. Here’s a step-by-step guide to bleeding a radiator safely and effectively.

Tools and Materials You’ll Need

  • Radiator key (or a flathead screwdriver for some modern radiators)
  • Cloth or towel
  • Container or bowl to catch water
  • Gloves (optional for protection)

Step 1: Turn Off Your Heating System

Before you start, make sure to turn off your central heating system. This will prevent more air from being drawn into the system and allow the radiators to cool down, reducing the risk of burns.

Step 2: Locate the Radiator Bleed Valve

The bleed valve is usually found at the top of the radiator, on either side. It looks like a small valve or screw. Older radiators typically require a radiator key, while some modern ones might use a flathead screwdriver.

Step 3: Protect Your Floor

Place a cloth or towel under the bleed valve to catch any drips of water. Have a container or bowl ready to catch any water that might escape when you bleed the radiator.

Step 4: Open the Bleed Valve

Insert the radiator key or flathead screwdriver into the bleed valve and turn it counterclockwise. You should hear a hissing sound as the trapped air escapes. Turn the valve slowly and only a quarter to half turn to avoid water gushing out.

Step 5: Release Trapped Air

Let the air escape until water starts to flow out steadily. This indicates that all the trapped air has been released. Once you see a steady stream of water, close the bleed valve by turning the key or screwdriver clockwise.

Step 6: Tighten the Bleed Valve

Ensure the bleed valve is tightly closed, but do not overtighten it, as this can damage the valve. Wipe away any excess water with your cloth or towel.

Step 7: Check the System Pressure

After bleeding the radiators, check the pressure gauge on your boiler. Bleeding the radiators can sometimes cause a drop in system pressure. If the pressure is too low, you will need to top up your boiler’s water pressure to the recommended level. Consult your boiler’s manual for instructions on how to do this.

Step 8: Turn Your Heating System Back On

Once you’ve bled all the necessary radiators and checked the system pressure, turn your heating system back on. Allow the radiators to heat up and then check them to ensure they are warming evenly. If you still notice cold spots, you might need to bleed the radiators again.

Tips for Effective Radiator Bleeding

  • Start with the Radiator Farthest from the Boiler: Begin bleeding the radiator farthest from the boiler and work your way towards the nearest one. This ensures that air is removed systematically from the system.
  • Bleed Regularly: Regularly bleeding your radiators can help maintain an efficient heating system. It’s a good practice to bleed your radiators at the start of the heating season and periodically throughout the winter.
  • Monitor Performance: If you frequently find air in your radiators, it might indicate a more significant issue with your heating system, such as a leak or a problem with the boiler. In such cases, it’s best to consult a heating engineer.


Bleeding a radiator is a straightforward task that can significantly improve the efficiency and performance of your heating system. By following this step-by-step guide, you can ensure your radiators are working effectively, providing a warm and comfortable environment in your home. Regular maintenance like this helps extend the life of your heating system and can save you money on energy bills.