How to Bleed a Radiator Boiler How to Bleed a Radiator Boiler

What You'll Need
Hexagonal bleed key
Phillips head screwdriver

If air gets into your radiator boiler system, it can create problems for the system and cause damage to both the boiler and radiator. In order to fix the problem, you will have to get the air out of the system using a process known as "bleeding." If your radiator isn't heating evenly, or if it isn't heating at all, or if you start to hear pounding sounds coming from the pipes around the system, it may be a sign of air in the boiler. Read on for a brief guide on how to bleed a radiator boiler to remedy these problems.

Step 1 -- Turn Off the System

Before you can begin to bleed the radiator, you'll need to first turn it completely off. Turn the heating system off at the central controls, and ensure that both the radiator and the boiler are turned off. This will protect the system when you're bleeding it and will help to make sure that no additional air can be let in while you work.

Step 2 -- Prepare the Bleeder Screw

Remove the front cover of the radiator with a screwdriver. The bleeder screw is located on the front panel of the radiator and underneath the protective front cover. It will be removed with the hexagonal bleed key. Before you do this, however, place a bowl underneath the bleeder screw to catch any water that comes out. Wrap the screw fitting in cloth to absorb water as well.

Step 3 -- Open and Close the Screw

Use the bleed key to turn the bleeder screw about one half of a turn counterclockwise. You'll hear the radiator hiss a bit as air is let out from inside of the pipes. Watch for water to begin to trickle out of the radiator screw. As soon as it does, you need to turn the screw back to the original position by rotating it another half turn clockwise.

Step 4 -- Attach the Hose

Look for the hose bib on the front of the boiler. Close the gate valve from the boiler to the bib, then fasten the hose to the front and place the other hose into a bucket.

Step 5 -- Flush the System

Open the bib valve to allow water to drain from the radiator. Then, while the water is filling the bucket, activate the water fill valve. Allow the system to continue to flush out until no more air bubbles can be seen in the water that comes out of the hose. Finally, open the gate valve once again to completely bleed any remaining air from the boiler system. Close the hose bib and remove the hose from the front of the boiler. Discard the water.

Allow the radiator to fill up again, and then shut off the water valve. Set the thermostat so that the radiator begins to work again and check for signs of air in the system.

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