How To Bleed A Radiator

It is easy to work out when your radiators should be bleed, as the top area will feel cool to the compared to the lower area and in some severe cases, the entire radiator will remain cold when the heating system is turned on. This is because trapped air replaces the water that normally heats the radiator.

When you “bleed the radiator” you are releasing this air allowing the hot water to flow freely again.

How Does The Air Get Into A Heating System?

Air can be introduced into the central heating system in several ways. This can occur when new water enters the system from the expansion tank or undergoes routine maintenance.

Conventional Boilers

Preparing To Bleed Your Radiators

If your house has 2 or more floors, you’ve got to start at the downstairs radiators first. It is also recommended to start with the radiator furthest from the boiler. Move to the next floor when you are finished bleeding all the radiators downstairs.

Make sure you’ve turned the central heating system off before bleeding the radiators. This is important because some pumps, depending on the type of system you have, will pull more air into the system as you work. Be safe turn the system off.

How To Bleed Your Radiators

You need a radiator key, a towel or some sort of rag and a container to catch any water from the radiator. If you do not have radiator keys, you can pick them in any DIY store for a very reasonable price. You may be able to use a pair of pliers, but at the risk of damaging the valve, it’s not recommended.

Before starting, make sure your central heating is turned off. It can be risky; the last thing you want is boiling water flooding out of the valve.

You should see a square “bleeding screw” on top of the radiator. This is the part that you need to open to release any trapped air from the system.

Anti-Clock To Unlock

Turn the bleed screw anti clockwise and use the cloth to keep any errant water from your floor. You should hear a slight hissing noise as air leaves the heating system.

Once the hissing stops and there is only water in the radiator, use the radiator key again to tighten the bleed screw, making sure not to over-tighten. You’ll have to do this again next year.

Guide to Biomass Boilers

Repeat the process again for all the radiators in your house.

After you’ve bled all the radiators, you can turn on the heating system again. It is good practice to check the pressure gauge in the boiler to ensure that it is at the optimal level (about 1 / 1.5 bars) and that the radiators all heat up evenly.

It may be necessary to bleed for some radiators more than once. If this still does not solve the problem, you may need a professional engineer to take a look at your system.

Proper Heating System Maintenance

If your heating system is slow to heat up due to trapped air, it means that your boiler has to work harder to heat your home, adding to your monthly energy bills. By keeping a well-maintained system, you can not only keep your energy bills to a minimum but also avoid damaging your boiler over time.

Whilst bleeding your radiators is essential, we also recommend that you

  • Get a regular boiler heat pump service
  • In the summer months, try to use your heating system occasionally to keep things running smoothly.
  • Keep an eye on your heating system for minor problems, such as pressure drops or small leaks.

Last Updated on April 11, 2021


Author: Indra Gupta

Indra is an in-house writer with a love of Newcastle United and all things sustainable.

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