How to Bleed a Boiler & Radiator

Written by cameron easey
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A hot water system that uses a boiler and radiators to provide heat requires yearly maintenance, which will require you to bleed the system. When a hot water system has been running for long periods of time air can get into the system, which will need to be purged. Before bleeding a radiator and boiler, turn off the boiler.

Skill level:

Things you need

  • Small bucket
  • Radiator bleeder key
  • Garden hose

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    Bleeding the Radiator

  1. 1

    Turn off the boiler to your heating system.

  2. 2

    Place a small bucket on the side of the radiator under the bleeder valve.

  3. 3

    Insert a radiator bleeder key into the bleeder valve of the radiator.

  4. 4

    Turn the bleeder key counterclockwise half of a turn to open it. When the valve opens there will be a hissing sound as air escapes.

  5. 5

    Turn the bleeder valve clockwise half a turn to close it when water starts to leak out of the valve.

  6. 6

    Repeat steps 1 through 4 on the rest of the radiators for the heating system.

    Bleeding the Boiler

  1. 1

    Attach a garden hose to the drain valve on the boiler.

  2. 2

    Place the hose in a bucket or a drain on the floor, or run it outside.

  3. 3

    Open the fill valve to let water into the boiler and then open the drain valve. Open the valve by turning it clockwise.

  4. 4

    Let the water drain out of the boiler until no air bubbles come out of the garden hose.

  5. 5

    Close the drain valve and the fill valve. You can then remove the garden hose and turn the boiler back on to complete the project.

Tips and warnings

  • Clean up any water that has got onto the floor with a rag or towel.
  • If you do not turn off the boiler the hot water coming out of the radiator or boiler can cause burns.

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