Venting the heating system – we explain just how simple it is

When it starts to get colder outside, you will inevitably want to turn on your radiators. When you first open your radiator, you often get annoying intermittent water flow and gurgling noises. This is caused by air in the radiators. Another clear indication of this is when your heating system does not fully heat up, i.e. radiators stay completely or partially cold. What’s the proper way to fix this? Venting the heating system. We explain just how simple it is.

Bleed key to vent your heating system

Venting the heating system – what you need

  • a glass, a cup or a mug
  • some rags or a cloth
  • a bleed key, which can be supplied by your heating contractor at low cost, or easily purchased from any hardware store.

Before beginning the actual venting process, first turn the radiators on to their highest level. If you are the homeowner, you should also turn the circulation pump off if possible. Now wait about 30 minutes, so that any air bubbles can collect in the radiators.

Bleeding radiators

1. Place the rags under the radiators so that they will catch any water that leaks from the bleed valve. Alternatively, you can wrap the rag directly around the bleed valve.

2. Now insert the key and hold the container under the bleed valve. Slowly open the valve with the key, but do not open fully. It usually takes half a turn or less before you hear it hissing. PLEASE NOTE: The escaping air may be hot so keep a safe distance.

3. When the hissing becomes quieter and finally stops, water will start leaking. The radiator is now bled and you can close the bleed valve.

If you shut off the circulation pump, don’t forget to turn it back on. Also check whether the water pressure in the heating circuit is still adequate.

It may be necessary to perform the venting process more than once.