How to Bleed Airlock Radiators

Updated February 21, 2017

A hot water heating system relies on the ability of hot water to flow freely through the radiator. If you discover that one or more radiators in your home is not heating properly, the culprit may be something as simple as trapped air. Once an airlock occurs, it will prevent hot water from travelling through the radiator. Fortunately, bleeding the air out of a radiator does not require the aid of a heating professional. Removing the air from a radiator is a job most homeowners can effectively handle on their own.

Locate the radiator that is positioned the greatest distance away from the boiler. If you have a two-story house, this usually means you'll start with a radiator on the second floor.

Locate the bleeder valve on the radiator. If the radiator is a baseboard-style radiator, you may have to remove the end-piece from the radiator. In most cases, this will require the removal of a couple screws. The bleeder valve on baseboards will be found near where the water pipe emerges from the floorboards. On standing radiators, the bleeder valve is often located at the top, on either the left or right side.

Position a small container beneath the bleeder valve. A cup or small plastic storage container will suffice. The container will catch any water that escapes the bleeder valve.

Open the bleeder valve. How you open the valve will depend on the type of radiator. Most will require a simple screwdriver. Some, however, will have a specific bleeder valve key. Others will require a small socket. Whatever the tool required, turn the bleeder valve counterclockwise to open it. Water should begin to dribble out as the valve is opened. If your radiator is airlocked, small bursts of air will also emit from the valve. Allow the valve to remain open until it releases only water.

Close the bleeder valve by turning it clockwise with the screwdriver, radiator key or socket. Move the next radiator in succession and bleed it as well. Continue bleeding each radiator in the home, working your way closer to the boiler. Once you've bled all the radiators, go back to the first radiator. Open the bleeder valve. If it releases only water, you're done. If air escapes, you must continue bleeding each radiator in the home until all air has been removed.


Avoid draining too much water from the system when bleeding your radiators, as this may cause a drop in the boiler's water pressure. If the water pressure gets too low, add more water by opening the fill valve above your boiler. In most cases, the amount of pressure required is between 5.44 and 6.8kg. In some cases, the bleeder valve may have accidentally been painted over, thus blocking the hole through which air and water are released. Use a small needle or piece of wire to poke a hole through the layer of paint and open the bleeder valve.


The water released from the bleeder valve may be hot, especially if the boiler is running or recently ran.

Things You'll Need

  • Small container
  • Screwdriver, radiator key or socket set
  • Needle or small piece of wire, if necessary
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About the Author

Arthur Barnhouse has written numerous short stories, contributed content to various websites and was an invited speaker at a university symposium on creative writing. He began writing in 2002 and holds a Bachelor of Arts in English literature from the University of Pittsburgh. Barnhouse has driven across the United States numerous times and draws upon his travel experiences in his writing.