This procedure is for hot-water radiators with a designed bleed valve. It does not apply to electric radiators or steam systems without following their specific instructions.
Turn the heating off and let it settle
Avoid opening a bleed point while a pump is moving very hot water. Wait until the radiator is safe to handle and place a cloth or cup beneath the valve.
Open the valve only slightly
Use the correct key and turn slowly. Trapped air usually produces a hiss. Do not remove the bleed screw completely.
Close when water runs steadily
Once the air stops and a stable small flow appears, close the valve without overtightening. Dry the area and verify that it does not drip.
Check system pressure when applicable
Bleeding can lower pressure. Use the boiler/system manual for the correct range; do not refill blindly or operate valves you cannot identify.
Repeated air is a diagnostic clue
Frequent bleeding can point to incorrect pressure, leakage, expansion-vessel problems, or air entering the system. A completely cold radiator can also have a closed valve or circulation issue.
Bleeding is a specific fix for trapped air, not a task to repeat on a schedule without symptoms.
Sources
- U.S. Department of Energy — Home Heating Systems — Heating-system operation, efficiency, controls, and maintenance.