How to Remove Air from a Combi Boiler

Combi boilers are relatively simple to use and look after, but what do you do if air becomes trapped in your boiler?

This is known as an airlock, but thankfully they are relatively easy to deal with and you won’t need to worry about forking out for a new boiler. 

What is boiler airlock?

A boiler airlock refers to when there is air trapped within the boiler in a singular location. 

Airlocks can cut off a consistent water supply and stop the flow of water to specific areas of your central heating system. 

What happens if air is trapped in a combi boiler?

If left untreated, airlocks can cause damage to a boiler and other components, such as the pump and pressure gauge. 

It’s vital that you have a heating engineer examine your boiler as soon as possible, otherwise the airlock may cause your boiler to not work at all. 

How to detect boiler airlock

When air is trapped in a combi boiler, you may notice a few different signs that something isn’t quite right. These potential signs include:

• No hot water from taps and showers
• Spluttering or inconsistent flow from taps
• Cold spots on radiators that are usually fine 
• Tapping and banging sounds 
• Lower than normal boiler pressure

If you notice one or more of these issues present, there is a strong likelihood that there are one or more airlocks in your combi boiler. 

Will an airlock in a boiler clear itself?

It is quite rare for an airlock in a boiler to clear itself, so it is essential that the issue is addressed as soon as possible. If it goes untreated, airlocks can cause serious damage to your boiler. 

1. Prepare the area – Lay a few dry towels beneath the radiator you’re working on to catch any water. Make sure to keep your bleed key and any additional tools handy too.

2. Locate the bleed valve – Once your boiler is turned off and the system has cooled down, locate the bleed valve. This is typically found at the top of the radiator.

3. Open the valve – Insert the radiator bleed key into the valve and turn it slowly to release the trapped air. If you hear a hissing noise, this is the air escaping from the system.

4. Close the valve – Once the hissing sound stops and water begins to flow from the valve, close it by turning the key clockwise. Once complete, check and adjust the boiler pressure is necessary and refill the system. 

The garden hose method 

Another method you can use to get rid of an airlock is by using the garden hose method. You will need an outdoor tap and a suitable length hosepipe. 

1. Prepare the pipework – Turn off the mains water supply and locate the stopcock valve. This can usually be found by the kitchen sink. Next, open all the hot water taps in your home to drain the system.

2. Connect the hose – Attach one end of the garden hose to the outdoor tap and the other to the lowest hot water tap in your home – this may be in a downstairs bathroom or the kitchen. Securly fasten both ends with duct tape.

3. Force water through the pipes – Turn on the outdoor tap, allowing water to flow through the hose and back into the water system. The pressure from the hose will dislodge any trapped air and hopefully clear the airlock.

4. Drain and disconnect – Once the airlock has been cleared, turn off the outdoor tap and disconnect the hose. Next, turn back on your main water supply to refill the hot water system. Don’t forget to reopen the stopcock, close all the hot water taps and check the boiler pressure. 

If you don’t have any success with either of the methods above, or you simply don’t feel comfortable doing it yourself, get in touch with our team at Lacey Plumbing & Heating and we will be more than happy to help you remove the airlock.