Air in your radiator prevents hot water from reaching all parts. This leads to cold spots and less heat output. When you bleed your radiators regularly, efficiency increases by up to 15%, and your heating system runs more quietly.
Step by step
Every radiator should contain only water, no gas. If air gets in during installation or later, an air pocket forms at the top of the radiator. Water can't flow higher, the radiator stays partially unheated. Your boiler valve must work harder, energy consumption increases. Through the bleeding valve (at the top of the radiator) you release this air so only water circulates in the system.
Source: VdZ Forum Wohnenergie, Air in radiators reduces heat output by up to 15%
Step by step
- Identify your radiatorsPick a radiator that doesn't warm up properly at the start of the heating season or is warm at the bottom but cold at the top. This is typically a radiator that hasn't been bled for a long time.
- Get a bleeding keyBuy a radiator bleeding key (costs €2–5) or use a flathead screwdriver. The bleeding valve sits at the top right or left of your radiator with a small screw or opening.
- Catch water under the valvePlace a small container or cloth under the valve. Turn the screw slowly counterclockwise with the key, you'll hear a hissing sound as air escapes.
- Let air out until water comesKeep the screw open until you hear no more hissing and water comes out without air bubbles. This takes 20–30 seconds per radiator. Then close it right away.
- Go through all radiatorsRepeat with every radiator in your home, starting with the top floor or the room farthest from the boiler. Do this once per heating season or when radiators won't warm up.
Worked example
Before: Living room radiator: bottom 60 °C, top only 30 °C, runs the whole time loudly / hisses
After: After bleeding: radiator heats evenly at 55–60 °C, runs quietly, heat output noticeably higher. Whole system uses less fuel for the same temperature → about 2–3% savings per radiator, with multiple radiators 10–15%