The Met Office has warned of colder weather over the coming weeks, and during cold spells a common heating issue is trapped air in radiators. This can cause strange noises or leave radiators feeling cold at the top.
Bleeding your radiator lets this trapped air out, helping your heating work better and keeping your home warm. Here’s how you can do it safely at home.
What you’ll need
- A radiator key (available from most DIY shops or online)
- A cloth and a small bowl or container
- Gloves to protect your hands
How to check if your radiator needs bleeding
- Turn your heating on and let the radiators warm up.
- Carefully feel each radiator (they may be hot).
- If the top feels cooler than the bottom, or you hear bubbling or rattling sounds, it likely needs bleeding.
Step-by-step: how to bleed a radiator
1. Turn off your heating
Switch off your boiler and let the radiators cool down fully. This usually takes about an hour. Make sure all radiator valves are open.
2. Find the bleed valve
The bleed valve is usually at the top of the radiator, on one side. It looks like a small round hole with a square inside.
3. Protect the area
Place a bowl under the valve and hold a cloth behind it to catch any water.
4. Open the valve
Insert the radiator key and slowly turn it anti-clockwise (about a quarter turn).
You should hear a hissing sound as air escapes.
5. Close the valve
When the hissing stops and water starts to come out, turn the key clockwise to close the valve. Do not tighten it too much.
6. Repeat if needed
If you have more than one radiator, bleed them all. Start downstairs and work your way up, as air rises through the system.
Check your boiler pressure
After bleeding your radiators, check your boiler pressure.
It should usually be between 1 and 1.5 bar when the system is cold.
If the pressure is too low, you may need to top it up using the filling loop (check your boiler manual for guidance).
Turn the heating back on
Switch your heating back on and check:
- Radiators are heating up evenly
- No unusual noises
- Your boiler is working normally
Need more help?
If this doesn’t fix the problem, or you need other heating advice, please get in touch with us and we’ll be happy to help.
Our Repairs Hub is very busy at the moment due to the cold weather. If you can, calling between 3–4pm or 5–6pm may mean a shorter wait.