How to Bleed a Radiator

A home radiator that is cold at the top and warm at the bottom usually is a sign of trapped air. The radiator needs to be bled. Sounds like an episode of Dr. G, Medical Examiner. Here’s how to bleed a radiator for a steam and hot water system.

Steam system

1. Turn radiator off. Give it time to cool down if it is not already cold.
2. Unscrew radiator air vent (looks like a mini-silo with numbers on its head). Shake out any trapped water and replace it.
3. Place a small pan and rags on floor where radiator is connected to the steam pipe.
4. Use pipe wrench to loosen connector. Disconnect radiator from the steam pipe.
4. Tilt the radiator (You’ll need help. The radiator is heavy cast iron) and drain any trapped water into the pan.
5. Reconnect
6. Slide a shim under the radiator so it tilts toward the connection pipe. This allows proper drainage for the steam return.

Hot water system

1. Turn the furnace off
2. Look for the bleed valve at the top end of one side of the radiator
3. Using a “bleed key” turn the valve counter clockwise slowly about a half a turn
4. You’ll hear the hissing sound of air escaping as your turn the valve. When water begins to come out close the valve.