How to Bleed a Radiator — Step by Step Guide

How to Bleed Your Radiators

Bleeding a radiator removes trapped air, which causes cold spots and reduces efficiency. It's a simple job anyone can do.

What You'll Need

• Radiator bleed key (available from any hardware store, ~£1)
• A cloth or small container to catch water

Step-by-Step Process

1. Turn off the central heating and wait for radiators to cool (30–60 minutes)
2. Identify the radiators that feel cold at the top — these have air trapped in them
3. Starting with the downstairs radiators, locate the bleed valve (a small square valve at the top, usually one end)
4. Insert the bleed key and slowly turn anti-clockwise (about a quarter turn) — never fully remove the valve
5. You'll hear a hissing sound as air escapes. Hold the cloth below to catch any drips
6. When a steady stream of water (not air) comes out, close the valve
7. Move to the next radiator and repeat
8. Once done, check your boiler pressure gauge. Bleed each radiator causes a small pressure drop — top up to 1.5 bar if needed
9. Turn the heating back on and check all radiators heat evenly