How to bleed radiators? - Bleeding radiators is a common maintenance task to ensure they work efficiently. Start by turning off the heating system and allowing the radiators to cool down. Locate the radiator bleed valve, usually found at the top of the radiator. Place a towel or container beneath the valve to catch any water. Insert a radiator key or a flat screwdriver into the valve and slowly turn it counterclockwise. You should hear a hissing sound as air escapes. Once water starts flowing steadily, close the valve. Check the pressure on your boiler if needed and turn the heating system back on.