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How to bleed a radiator

Knowing how to bleed a radiator will make all the difference for your heating this winter. If you turn up your heat, but find that one or more of your radiators are cold as a stone, it is very likely that they need to be purged. You can bleed a radiator by essentially letting the trapped air out that prevents water from heating the entire radiator.

Another sign that your radiators need to be purged is if they make clicking, clicking, or gurgling noises, which can be a common problem for many households. Similar to insulating your windows for the winter, knowing how to bleed a radiator will save you money on your energy bills because you won’t lose heat.

Luckily, bleeding a radiator is quick, easy, and it won’t cost a thing. Follow these simple steps to bleed a radiator and keep your home warm this winter.

Before starting, it is advisable to identify the radiators that need to be bled.

How to bleed a radiator to remove air

What you will need

A radiator bleed key

Small container or towel to catch water drops


Safety gloves

1. Check and diagnose your radiators – First of all, you will need to turn on your heating fully it therefore reaches its highest temperature. Run your hand along the top of each radiator to see if there are any cold spots. If you find radiators that have cold spots, these are the ones that need to be purged.

Feel the top of the radiator for cold spots

Feel the top of the radiator for cold spots (Image credit: Shutterstock)

2. Next, turn off your radiators and let cool completely. This is to avoid the risk of being scolded by the hot water inside the radiators.

3. Once you have identified the radiators to bleed, locate the radiator bleed valve which is usually on the upper end. This is usually a small screw or metal nut found inside a surrounding nut.

Radiator valve

Radiator valve (Image credit: Shutterstock)

4. To prevent messy spills from discoloring your floor, put old towels or a tray to catch water drops.

5. Insert your radiator key into the valve and slowly turn counterclockwise halfway to release air pressure. If you’ve lost your key, you can find a suitable replacement on Amazon, like the Wal-Rich Radiator Bleeding Air Valve key.

You should hear a hissing sound when you turn the valve, which means the trapped air is coming out. It is advisable to keep a container underneath to collect any residual water droplets.

Turn the valve and collect the water from the bleed of a radiator

Turn the valve and collect the water from the bleed of a radiator (Image credit: Shutterstock)

6. Once the valve begins to release a constant flow of water, it signals that the air is completely released, and you can now close the valve. Simply turn the valve clockwise to tighten it, and voila! You can repeat these steps for any other heater in the house that needs to be bled. Turn your heater back on and check that there are no cold areas above the heater.

Container for collecting water from the bleed of a radiator

Container for collecting water from the bleed of a radiator (Image credit: Shutterstock)

Other tips for bleeding a radiator

  • How often should I bleed my radiator? – It is recommended to bleed your radiators at least once a year. Especially before the arrival of the winter months so that you do not feel the cold.
  • How long does it take to bleed a radiator? – As a general rule, it takes about 20 to 30 seconds to bleed a radiator. But that will depend on the size of your radiator and how much air it contains.
  • What happens if my radiator is still cold after bleeding?– If you still find cold patches at the top, you may need to bleed again. However, if you experience cold spots at the bottom of your radiator, it may indicate a buildup of sediment inside the base. In this case, the whole system would need a flush, and you would need to hire a professional to do it.


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