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How To Bleed A Radiator

Bleeding a radiator refers to the process of removing air from your central heating system. This is an easy way to make sure your radiators are working efficiently, saving you money in the long run. Turn your heating on and see if the top of the radiator is just as hot as the bottom of the radiator. If the temperature isn’t consistent across the radiator, this indicates trapped air, which means that your radiator needs bleeding.

Signs your radiators need bleeding:

  • Pipes banging
  • Radiators gurgling
  • Cold patches at the top of your radiators

You will need the following items:

  • Radiator bleed key
  • A cloth to catch any water leakage
  • A small container or towel to place under the radiator
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Step 1  – Turn Your Heating On Full

The first step is to turn your heating on full and wait for all radiators to reach their maximum temperature.

Turn Your Heating On | How To Bleed A Radiator

Step 2 – Check Each Of Your Radiators For Cold Spots

Identify which radiators need bleeding by carefully running a hand across the top of each radiator to feel for any cold spots. If the temperature across the radiator is inconsistent, this is a good sign that the radiator needs bleeding.

Check Your Radiators For Cold Spots | How To Bleed A Radiator

Step 3 – Turn Your Heating Off & Allow It To Cool Down

Once you have checked all your radiators and identified which ones need bleeding, turn off your heating and allow the radiators to cool down. This is to ensure that that you don’t get burnt by any hot water whilst bleeding the radiators.

Step 4 – Find The First Radiator To Bleed

If you need to bleed more than one radiator, always start with the one that is furthest away from your boiler.

Step 5 – Locate The Radiator Bleed Valve

Radiator bleed valves look like a small metal square or screw found inside a surrounding nut, and are usually located at the top end of the radiator.

Locate The Bleed Valve | How To Bleed A Radiator

Step 6 – Place A Small Container or Towel On The Floor

Place a container or towel on the floor underneath the bleed valve to catch any drips of water.

Step 7 – Insert The Radiator Bleed Key

Take your radiator bleed key and insert it into the bleed valve until they have locked together.

Insert The Bleed Key | How To Bleed A Radiator

Hold your cloth next to the valve and under the little drain hole and be ready to catch any drips.

Step 8 – Turn The Bleed Key A Quarter (Anti-Clockwise) Turn

Slowly turn the key anti-clockwise to open the valve.  You should hear a hissing sound as trapped air escapes.

Valve

Once the hissing noise stops and water starts to leak out, close the bleed valve by turning  the key clockwise into its original position. 

Close The Radiator Valve | How To Bleed A Radiator

Make sure you don’t close the valve too tightly as you may damage the valve.

Step 10 – Bleed Your Other Radiators

Repeat steps 5 – 9 for any other radiators that need bleeding.

Step 11 – Check The Pressure of Your Boiler

If you have a pressurised central heating system, you may notice that the pressure gauge on your boiler may have dropped following bleeding of your radiators.

Check Your Boiler Pressure | How To Bleed A Radiator

If this is the case, you will need to top the boiler pressure up before turning your heating back on.

Step 12 – Turn Your Heating Back On For Final Checks

Once your boiler pressure is back to normal, you can turn your heating back on.

Give your radiators time to heat back up again and check to see if there are any cold spots by following Step 2.

If you find that there are still cold spots at the top of your radiators, try bleeding them again.

If you’re still unsure of how to bleed your radiators, book an appointment with a qualified gas engineer by calling our team on 0800 014 7199

Frequently Asked Questions

Should the heating be On or Off when you bleed the radiator?

You should always bleed your radiators when the heating is switched off and the system is cool. Bleeding radiators with hot water flowing through the system increases the chances of scalds and burns.

Which radiator should you bleed first?

You should always start bleeding radiators with the radiator that is furthest away from the boiler.

How often should you bleed your radiators?

Hot water radiators should be bled at least once a year.

It is always best to do this well in advance of the winter months so your system can be ready and in full working order before the cold weather sets in.

How long does or should it take to bleed a radiator?

Bleeding an average size radiator shouldn’t take more than 20 to 30 seconds to bleed fully.

The size of the radiator and the amount of air trapped inside will obviously affect the time it takes to bleed them.

Simply carry on bleeding the radiator until the hissing noise stops or water starts to run out of the bleed valve.

Where can I buy a radiator key from?

Radiator keys are easy to find in most hardware stores or even supermarkets and range in price from 50p to £5.

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