As autumn temperatures drop and central heating systems kick back into daily operation, trapped air inevitably collects at the top of upper-floor radiators. This trapped air prevents hot water from circulating efficiently, forcing your boiler to burn more gas while leaving rooms uncomfortably chilly at eye level.
Preparing Your Tools and Protecting Your Floorboards
Bleeding a radiator requires nothing more than a solid brass radiator key and a heavy cotton rag or small container to catch water droplets. Avoid cheap stamped metal keys that wear down easily and round off delicate square valve pins over time.
Before opening any valves, ensure your central heating system is switched off completely and allowed to cool for at least thirty minutes. Bleeding radiators while the circulating pump is active risks sucking additional air into the pipework system.
Executing the Bleed and Checking System Pressure
Insert the key into the bleed valve at the top corner of the radiator and slowly turn it anti-clockwise by a quarter turn until you hear a clear hissing sound. As soon as a steady trickle of water replaces the escaping air, tighten the valve firmly without over-torquing the thread.
Once all radiators are clear, check your combi boiler pressure gauge. If the pressure has dipped below one bar, use the filling loop underneath the boiler to restore pressure to between one and one-and-a-half bar for optimal heating efficiency.