If your radiator is warm at the bottom but cold at the top, trapped air is preventing hot water from circulating fully. Bleeding releases the air and restores full heat output. Here's how to do it safely.
What you'll need
Step-by-step
**Step 1: Turn your heating on.** Run the heating until all radiators are up to temperature. This allows you to identify which ones need bleeding and confirms the trapped air is present.
**Step 2: Turn the heating off and wait.** Once you've identified the problem radiators, switch the heating off and wait 30 minutes for the system to cool slightly. This prevents scalding water spraying out when you open the bleed valve.
**Step 3: Find the bleed valve.** The bleed valve is a small square-headed brass fitting at the top end of the radiator. Some have a flat-headed screw you can use a screwdriver on, but most require the bleed key.
**Step 4: Open the valve.** Hold the cloth underneath the valve. Insert the bleed key and turn it anti-clockwise about a quarter turn. You should hear a hissing sound as air escapes. Keep the key in the valve.
**Step 5: Close when water appears.** As soon as water starts trickling out (it may be slightly discoloured — that's normal), turn the key clockwise to close the valve firmly. Don't overtighten.
**Step 6: Check boiler pressure.** Releasing air from radiators can reduce the system pressure slightly. Check your boiler gauge — it should read between 1 and 1.5 bar. If it's dropped below 1 bar, re-pressurise following your boiler manual.
**Step 7: Turn heating back on.** Test the radiator — it should now heat evenly from top to bottom.
When to call an engineer
If your radiators need bleeding repeatedly, it suggests air is entering the system — possibly through a leak or a faulty automatic air vent. Call a heating engineer if the problem recurs more than once a year.
NBS Plumbing & Heating — Sutton Coldfield — **07507 133204**.