How to Bleed a Radiator
Updated: Sep 9, 2024
Regardless of how shiny and expensive your radiator is, it is highly likely that it will require bleeding at some point, which is an inevitable part of maintaining your radiators and heating system. As we run our heating systems, it is very normal for air to build up in a radiator, but when this trapped air is left, it can prevent heat from being evenly distributed, and a radiator from running efficiently. If your radiator takes longer than usual to heat up, is noisy whilst doing so, or isn't hot from top to bottom, then it may require bleeding.
What Does 'Bleeding a Radiator' Mean?
Bleeding a radiator is the process of releasing trapped air from inside the radiator to improve its efficiency. To bleed a radiator, a special key is used to open a valve at the top, allowing the air to escape. Once the water starts to flow out, the valve is closed, ensuring the radiator is working efficiently again.
When Should You Bleed a Radiator?
You should bleed a radiator when:
Cold spots: If the radiator is warm at the bottom but cold at the top, trapped air may be preventing heat from circulating.
Noisy radiator: Gurgling, hissing, or banging sounds could indicate air in the system.
After turning the heating on: When you switch your heating back on after a long period (like after summer), air may have accumulated in the radiators.
Inefficient heating: If rooms aren't warming up as quickly as they should, the air in the radiator may be reducing its efficiency.
Annual maintenance: It's good to bleed radiators once a year, especially before the cold season, as part of regular home heating system maintenance.
How to Bleed a Radiator
Here we’ll explain how to quickly and simply bleed a radiator:
What you’ll need:
A radiator bleed key or flathead screwdriver
Old towels or a container to place underneath the radiator
A towel or rag to clean up any spillages
Steps:
1. Turn on your central heating.
Once your radiators are hot, you will be able to identify and make note of which radiators need bleeding by feeling for cold spots and listening out for any odd or gurgling sounds.
2. Turn off your central heating
Before proceeding to bleed any radiator you must remember to turn off the central heating system and then wait for the radiators to completely cool. Water in hot/warm radiators will not only be hot but also under pressure.
3. Locate the bleed valve and gather the bits you will need.
Bleed valves are typically located at the top of the radiator at one end, and will look like a round hole with a square in the middle of it.
4. Place your old towel/container just below the valve.
Do so to prevent the water that will come out from damaging the wall or flooring. Be aware that on some valves there is a tiny outlet, which could be positioned anywhere - so make sure to have a proper search for one, or you could end up with a messy wall.
5. Slowly turn the bleed screw anti-clockwise to bleed.
If you’re using a bleed key it should fit over the square vent a bit like an old clock key, whereas a flathead screwdriver will fit into the groove. Once engaged, slowly turn the vent anticlockwise until you can hear a hissing sound. Please be aware not to open the valve all the way, once the air has been bled from the radiator, water will follow.
6. Keep the valve open until the hissing stops.
Once the hissing stops and only water comes out, quickly close the valve and retighten it. Mop up any leakages and excess water.
7. Repeat steps 1-6.
Repeat the above steps on each radiator that needs bleeding.
8. Turn the central heating system back on.
Remember to check if the radiators are now heating up evenly, quickly and with no noise.
If bleeding the radiator doesn’t improve or solve any of these issues, especially if you’re bleeding it frequently, it is likely that there may be a more serious issue that should be looked at by a heating professional.
