Most new homes have forced hot air heat or baseboard heating systems, which replaced cast iron radiator heat. Cast iron steam radiators, usually found in older homes require periodic maintenance. Cast iron radiators heat a home by circulating hot water through the unit and radiating heat into a room. The radiators rely on a constant supply of water through the system. When air enters the heating system, it lowers the heating output. If radiators remain cool or cold, the system requires bleeding, which is the release of trapped air.
Turn the wall thermostat up 10 to 15 degrees to circulate the water through the pipes. This will cause much of the trapped air to accumulate in one radiator.
Lower the wall thermostat setting as far as possible to stop the flow of water through the heating system. Allow the radiator to cool to room temperature.
Lay an absorbent rag or large towel on the floor under the radiator. Place a bucket next to the radiator under the air vent.
Locate the air vent valve at the top of the radiator. The air vent valve looks like a slotted screw head.
Turn the valve counterclockwise with a flat-head screwdriver or a vent key, which is a key-shaped piece of metal made to fit the air vent release. Begin with the radiator furthest from the furnace and work your way down the system. The valve will sputter and spit water as the air releases. Once the noise stops and water streams gently from the valve, turn the valve clockwise to close it.
Move to the second furthest radiator and repeat. Continue to move in succession down the line until you bleed the water from all radiators.