Bleed Boiler

How to bleed your oil boiler after running out of heating oil?

Bleeding your oil boiler is a common task for homeowners. We have all been there, the radiators aren’t warming up and we come to the realisation that you have just ran out of heating oil! There are a number of key steps which should be taken to prevent impact to your system. This process, which is very simple, and takes less than five minutes to complete can be carried out by yourself if you are confident enough. If in any doubt contact an OFTEC Heating Engineer who can show you how to bleed your oil boiler . 

Why do you need to bleed the boiler? 

Basically this happens when the level of the oil falls below the fittings of the oil tank and air enters the oil line stopping the appliance from working. So once you get your tank filled up, the oil isn’t actually reaching the burner, which is why the boiler won’t fire. 

What will you need? 

  • Allen Keys – Usually 4mm
  • Screwdriver – This may be required to remove your burner cover
  • Oil Pads or rags – To absorb any oil which exits the bleed point
  • Torch – The oil usually seems to run out when it is dark and cold, so always have a torch at the ready

Steps to take when you think you have ran out of oil:

  • Check the heating oil in the tank – this may seem obvious, but the first step is to make sure a lack of oil is the issue. If there is no oil, place a delivery. 
  • Following delivery – allow the oil to settle for up to an hour as a fill of oil can disturb the water and sludge and this needs time to settle to the bottom of the tank prior to bleeding the boiler. 
  • Check if the burner has went to lockout – This is usually a red button on the front of your burner. Your burner has a mechanism inside it to stop it running when there is no oil present, this will be illuminated if combustion is not occurring. If nothing happens, move on to bleeding. 
  • Remove the outer casing of the burner – This casing is normally red (Riello Burner) and has two screws on it. These screws can either be allen keys or regular flat or star head screwdriver, so be prepared to have the right tools. 
  • Search for bleed point – This bleed point is usually on the left side of the burner. You will need a suitable sized allen key (usually 4mm) and a oil absorbent pad or rag to catch any oil. 
  • Bleeding the oil pipe – Unscrew the plug no more than half a turn and leave the Allen key in place. Then hold a oil pad or rag immediately under the plug to catch any oil which will be released. Be careful when rotating the plug  as it may come out of the bleed point and lead to a release of oil. The idea here is to let out any air, you will know you have let enough air out once the oil starts to appear at the bleed point. The plug should then be tightened to prevent any loss. 
  • Press the lockout button – The red button on the front of the burner should then be pressed again which should allow the burner fan to run and the boiler to fire. If the burner does not fire, repeat the bleed process to ensure all air has been removed from the oil line.
  • Screw the cover back onto the burner – This will be the last job you have to complete the process. Enjoy the heat.
  • Wash your hands – Always be sure to wash your hands after completing these works as it can cause skin dryness and irritation. 

After you have tightened up the plug at the bleed point, always be sure to dry an excess kerosene and keep an eye out for any leakage. 

Why is this process important?

This is very important because it not only helps remove any air trapped in the oil supply pipe, stopping your boiler from starting. It is also protecting your burner. If the lockout button is pressed repeatedly when your system is out of oil, this can cause damage to your burner. However, if the bleeding process is completed successfully, the operation of your oil fired heating system can continue to run smoothly without causing any damage to the burner and further issues. 

If you are in doubt don’t be afraid to give SSS Alleviate a call to help!

Images showing key locations on the burner

  • Lockout button – Yellow. 
  • Screws  to remove the burner cover – Green 
  • Bleed point – Red 
Bleeding your oil boiler
Bleeding your oil boiler
Bleed your boiler
Bleed your boiler

Did you know we specialise in Oil Heating? If you have noticed an urgent issue with your oil tank such as bulging or cracking, we urge you to contact us immediately or visit our page on oil leak response. If you are looking for oil tank removal or oil tank replacement contact SSS Alleviate to see how we can help. Contact us on 07391270659 or email

For government guidance on oil spills at home visit

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