How to Bleed a Baseboard Radiator

Radiators are designed to circulate hot water throughout your home, but air often finds its way into the system, creating pockets that block the flow. When you hear gurgling noises or notice that the baseboard remains cold while the boiler is running, you have an air lock. Clearing these lines is a fundamental maintenance task that ensures your heating system operates at full efficiency during the colder months. Performing this task requires a steady hand and a bit of patience. Done well, you will see a consistent stream of hot water escape the bleed valve, signaling that the system is pressurized and free of air. It is a quiet, rhythmic process that restores comfort to your living space without needing professional intervention.

1. Kill the System First. Switch off your thermostat or your boiler's power supply to stop the water pump. Wait at least 30 minutes for the water to stop circulating and the system to cool down.
2. Find Your Escape Hatch. Find the bleed valve on your baseboard unit, usually located at one end of the radiator behind the metal cover. You may need to remove a small access panel to see the valve clearly.
3. Armor Your Walls. Place a small container or a folded towel directly underneath the bleed valve. This catches the water that will inevitably spray out once the seal is broken.
4. Release the Trapped Air. Insert your radiator key or a flathead screwdriver into the valve screw. Slowly turn it counter-clockwise about a half-turn until you hear the distinct hiss of escaping air.
5. Switch From Air To Water. Hold the valve open until the hissing sound stops and a steady stream of water begins to flow. Close the valve immediately by turning it clockwise until snug.
6. Balance The System Pressure. Walk to your boiler and check the pressure gauge. If the pressure dropped below 12-15 PSI, you may need to open the water feed valve briefly to add more water to the system.