Cold at the top, warm at the bottom? Your radiator has trapped air inside and needs bleeding. It takes about 5 minutes and costs nothing. Here’s exactly how to do it.
What You’ll Need
- A radiator bleed key (costs about 1$ at any hardware store)
- An old cloth or small towel
- A bowl or tray (optional)
Step-by-Step Guide
Step 1: Turn the heating on Switch your heating on and let it run for about 15 minutes until all the radiators are warm.
Step 2: Identify which radiators need bleeding Run your hand carefully across each radiator. If the top is noticeably cooler than the bottom, it needs bleeding.
Step 3: Turn the heating off Switch the heating off and wait about 20 minutes for the system to cool slightly. The pressure will be lower and the water won’t be scalding hot.
Step 4: Find the bleed valve The bleed valve is a small square nut at the top corner of the radiator.
Step 5: Open the valve Insert the radiator key and turn it anti-clockwise about half a turn. You’ll hear a hissing sound as trapped air escapes. Hold your cloth underneath to catch any drips.
Step 6: Close the valve As soon as water starts to trickle out, the air is gone. Turn the key clockwise to close the valve firmly — but don’t overtighten.
Step 7: Check your boiler pressure Bleeding radiators can lower your boiler’s pressure. Check the gauge and repressurise if it’s dropped below 1 bar.
Step 8: Turn the heating back on Switch the heating back on and check that the previously cold spots are now warm.
How Often Should You Bleed Radiators?
Once a year is usually enough — ideally at the start of autumn before you need the heating regularly. If you notice cold spots returning sooner, bleed them as needed.
That’s it! A 5-minute job that can make a real difference to your home’s warmth and your energy bills.