To encourage your heating system to work at optimum efficiency, it is important to bleed your radiators on a regular basis. Though it may sound difficult to bleed a radiator, it is actually quite easy to do. There is no special training required, and all you need is a radiator key and a small bowl.
If the heat in your home isn’t circulating well or the bottom portion of your radiator is warm while the top portion is cold, there may be air trapped inside the radiator. When this happens, it reduces the radiator’s ability to heat effectively. This trapped air may even lead other parts of your heating system to function poorly. Sometimes, most of a radiator will fill with air, and in such a case, there will be no noticeable temperature difference — the whole radiator will be cool to the touch.
As you prepare to bleed a radiator, you will most likely be starting with a system that has been turned on. As such, there should be warm water in the radiator. Before you begin, turn the central heating system off.
You’ll need to have a bleed key to bleed a radiator. If you don't have one, you may be able to buy a new one from a hardware store or use a flat screwdriver, if the bleed valve allows for it. This valve is typically positioned at the top of a radiator, near the end. Insert the bleed key or screwdriver into the bleed valve and turn it counterclockwise. Don’t turn it too much; a half a turn is usually enough.
As you turn the radiator key, the valve will open and you will hear a hissing sound. This is completely normal and is simply caused by the air escaping. Once water begins to leak out of the radiator, it is time to close the valve. To do so, turn the bleed key clockwise for half a turn. You can then move on to the next radiator that needs to be bled before turning your central heating system back on.
When you bleed a radiator, keep a small bowl or rag handy to catch the water that drips down. If you have a sealed heating system, be sure to do a pressure check and add water if needed. Once you’ve done so, you are finished and may turn your heating system back on. Store your bleed key until the next time you need it.