When to bleed a radiator

Let’s start by identifying the indications of a radiator that requires bleeding.
You may consider bleeding your radiator if:
1. Cold spots appear on your radiator when the heating is on.
2. There is a cold area at the top of the radiator.
3. The entire radiator remains cold.
4. You observe dirty, damp patches or mold developing on the walls, especially in less frequently used rooms.
5. Rattling or gurgling noises come from your radiator.

If you observe any of these signs, it’s probable that there is trapped air within your radiator, obstructing the circulation of hot water and preventing proper heating. Releasing this trapped air is necessary for efficient radiator heating. You should address the issue before it completely loses its ability to heat up.

How to bleed your radiator in 7 simple steps

Caution: Radiator water is very hot, so avoid burning yourself. Use protective gloves and clothing, and shield your floors as well.

You will need: a radiator key or a flat head screw driver and a container/cloth to collect water.
Now that you can recognize when your radiators require bleeding, follow our easy step-by-step instructions and bleed them.

1. Turn off the heating and wait for the radiators to cool down to a safe temperature.

2. Position a cloth under the radiator bleed valve.

3. Locate the bleed valve at the top corner of the radiator, which looks like a round hole with a square inside, and ensure there’s a cloth or bucket beneath to catch any water.

4. Insert the radiator key and turn it counterclockwise, listening for a hissing sound as air escapes.

5. Turn the radiator key clockwise to close the valve when the hissing stops and water begins to leak.

6. Repeat this process for any radiators that require bleeding in your home.

7. Check the boiler pressure after bleeding, as it may decrease. If the pressure is low, you’ll need to add pressure to your boiler.

Your FAQs answered

What should you do if nothing comes out when bleeding radiators, and there’s no air or water?

If nothing comes out when you bleed the radiator, it might be blocked with paint. Close the inlet and outlet valves on both ends of the radiator, then take out the screw from the center of the bleed valve. Insert the radiator key into the bleed valve and turn it counterclockwise slowly (a quarter-turn should suffice).

How often should you bleed radiators?

You should inspect all your home radiators every couple of months. We suggest doing this check before the cold weather sets in, to ensure your heating system works efficiently when you need it most.

Can you bleed a radiator while the heating is on?

Don’t bleed a radiator when the heating is on. It can be too hot to touch, and hot water might spray out, possibly causing burns. Always turn off the heating before bleeding a radiator. Also, bleeding when the pump is running can introduce more air into the system.

Can you use automatic radiator valves to bleed a radiator?

You might have automatic options for bleeding your radiators, such as using auto vents. These devices are connected to your radiator valves and release air slowly to maintain radiator efficiency. If you have an auto vent, manual bleeding may not be necessary.

How can I tell if radiator bleeding was successful?

After closing your radiator valves, you can safely turn on your central heating and hot water. If the bleeding was successful, your radiators should begin heating up within a few minutes, and the warmth will be evenly distributed. You can also inspect the pressure gauge on your boiler; it should ideally read between 1 and 2 bars.

How long does it take to bleed a radiator?

Typically, it should take 20-30 seconds to bleed a radiator. The time may vary based on the radiator’s size and the amount of trapped air.