How to bleed a radiator (and fix your boiler pressure!), by B&Q on YouTube. 2 min 16 s.
- Video length
- 2 min 16 s
- Time to do it
- 15 minutes
- Difficulty
- Easy
- Steps
- 9
What you need
Steps
Turn off the heating and let the radiators cool completely. Hot water can scald you when it escapes from the valve.
Check the boiler pressure gauge first. Note the reading and compare it with the target range in your boiler manual, usually around 1 to 1.5 bar.
Find the bleed valve at the top corner of the cold radiator. It is a small square or slotted screw inside a round nut.
Hold a cloth under the valve and fit the radiator key onto the square spindle. Turn it anticlockwise about a quarter to half a turn.
Listen for the hiss of escaping air. Keep the valve open until water dribbles out steadily, then close it clockwise straight away.
Wipe any drips and repeat on each radiator that feels cold at the top. Work through the house one radiator at a time.
Check the boiler pressure again. If it has dropped below the target range, connect the filling loop and open the valves slowly.
Watch the gauge and close the filling loop as soon as the needle reaches the target pressure. Do not leave it connected.
Switch the heating back on and check that every radiator now heats evenly from top to bottom.
Tips and common mistakes
Only open the bleed valve a small amount, or water will spray out and stain the wall.
Never bleed a radiator while the heating is running, as hot water can burn you.
If pressure keeps dropping after topping up, call a Gas Safe registered engineer rather than keep refilling.
Do not overfill the boiler, as pressure above the manual's range can trigger the safety valve.
Questions
How do I know a radiator needs bleeding?
It feels cold at the top and warm at the bottom, or you hear gurgling when the heating comes on. Bleeding releases the trapped air.
What if no water comes out of the bleed valve?
Air may still be escaping, so keep the valve open a little longer. If nothing changes, the valve may be blocked or the system may need a professional check.
Can I bleed a radiator without a radiator key?
A small flathead screwdriver fits some slotted valves, but a proper radiator key gives a better grip and is less likely to round the spindle.
This guide was drafted from the video's details and general task knowledge. It has not been checked against the full video. Check the video and relevant product instructions before following a procedure. Report a correction.
