How To Bleed A Radiator In 8 Simple Steps

Learn how to bleed your radiators in 8 easy to follow steps and ensure your central heating system is working effectively before the cold weather hits.

Bleeding a radiator increases the efficiency of your central heating system, lowers your energy use and bills, and improves the effectiveness of your radiators, helping you keep lovely and warm during the cold weather. It can also help keep your heating system in tip top condition, so you don’t get any chilly break downs. 

Tools You’ll Need To Bleed A Radiator 

•    A radiator bleed key – this is used to open the radiator vent valve and can be bought from most DIY stores. 
•    A cloth or towel to catch any water that comes out.

Bleeding a Radiator – Step by Step Guide

Step 1 – Turn on your central heating

Turning on your central heating system prior to bleeding your radiators will build up pressure in the radiator and help push any excess air out. 

Step 2 – Test your radiators for cold spots

To identify which radiators need bleeding, go through your entire home testing each radiator for any of the following:

  • Cold spots 
  • Gurgling noises
  • Takes a long time to heat up

These signs indicate that there is trapped air in the radiator which is preventing the hot water from filling the radiator, and so it will need bleeding.

Step 3 – Turn off your central heating 

Make sure you turn off your central heating system before attempting to bleed any of your radiators. If you don’t, the water will be extremely hot and you may burn yourself and/or release lots of water. 

Step 4 – Prepare the surrounding area

Protect the flooring around your radiator by laying old towels or blankets down. Some water may escape from the radiators and this can be discoloured, especially in older systems, so this is a vital step. 

Step 5 – Open the radiator bleed valve 

Take your radiator key and insert it into the radiator bleed valve, which is usually found at the top or bottom and to the side of the radiator and looks like a round hole with a square inside. You’ll feel the key and the radiator lock together. Carefully turn the value anti-clockwise about a quarter turn to release the air – it will begin to make a hissing noise. Ensure you keep a safe distance away as the air may be hot. 

Step 6 – Bleed the radiator 

Keep turning the valve key very slowly – if all the air escapes then water will soon follow – until all the air has been let out and you see a few drips from the radiator. Close the bleed valve by turning the key clockwise and being careful not to overtighten. 

Step 7 – Repeat the process

Repeat this process on each of the radiators you previously identified as needing a bleed. Remember, open and close the bleed valve very carefully as hot air and water may escape unexpectedly. 

Step 8 – Check the pressure of your central heating system 

Once you’ve bled your radiators, you’ll need to check if you need to repressurise your central heating system. This is because when you bleed radiators, you inevitably loose some water which can mean your system will struggle to heat your home effectively. Look at your boiler’s pressure gauge, it should be between 1.0 and 1.5 bar. 

To repressurise your system, you’ll need to turn the central filling loop that’s connected to your boiler, it looks like a tap, and slowly turn it to adjust the pressure.

If you need help bleeding your radiators or with the pressure in your heating system, get in touch with the friendly Expert Plumber team today on 01202 081141. Our certified, Gas Safe engineers are here to help with all your central heating issues, from installations to servicing to repairs