Boiler Airlock Causes and How To Fix an Airlock in Pipes

James Elston
Written by James Elston
Updated on 17th May 2024
Posted on 16th May 2024
Topic: Boiler Advice
Boiler Airlock Causes and How To Fix an Airlock in Pipes
air lock gas safe

Whilst boilers are relatively easy to use and look after, every now and then we get an issue that comes along as spoils our day. An airlock in a boiler, pipes or central heating system is just one of the many possibilities than can cause your boiler not to work.

However, if you do have an air lock, then you can breathe a very small sigh of relief that it isn’t going to cost an arm and leg to fix and you don’t need a new boiler or central heating system just yet.

Older boilers and central heating systems are more susceptible to costly repairs and problems, especially when out of warranty, so it’s always a good idea to get an annual boiler service or have something like central heating and boiler cover in place to prevent unwanted breakdowns or expenses.

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Anyway, let’s see what damage an airlock in pipes can cause.

What is an airlock?

An airlock in a boiler occurs when air becomes trapped within the heating system, preventing the flow of water through the pipes. This can cause a variety of issues, such as the boiler failing to heat up properly or strange noises coming from the pipes, or your boiler not working at all

Here are some frequently asked questions and answers about airlocks in boilers:

Boiler Air Lock Symptoms

There are several potential causes of an airlock in a boiler. It could be due to trapped air in the pipes, a build-up of sediment or debris in the pipes, or an issue with the water pressure in the system.

If you have a boiler airlock, you may experience the following symptoms:

No hot water

No hot water – One of the most common symptoms of a boiler airlock is that you won’t have any hot water. This is because the airlock is preventing the hot water from flowing through the pipes. Unfortunately this will be hard to determine without a full check up of your system but if this is the reason for not hot water from your boiler it is usually easily be fixed by a professional.

Low pressure

Low boiler pressure: Another symptom of a boiler airlock is that there may be little or no pressure in the system. This is because the airlock is preventing the water from flowing through the pipes and building up pressure.

To check this, have a look at your pressure gauge and read our guide on low boiler pressure for more information.

Weird noises

Strange noises: You may hear strange gurgling or bubbling noises coming from your boiler or pipes. This is a sign that air is trapped in the system and needs to be released. This is the biggest giveaway for an airlock but sometimes missed in older systems.


Water leaks: Airlocks can also be caused leaks in the system. This is because the air pressure can cause pipes or joints to become loose which let air in and leak water. A boiler leak is another issue on top of an airlock and is likely more cause for concern.

Read more about boiler leaks here

How to fix a boiler airlock?

To fix a boiler airlock, you need to release the trapped air from the system. One way to do this is to bleed the radiators, which involves opening a valve at the top of the radiator and allowing the air to escape.

Another method is to use a hose to force water through the system and push the air out. If you’re unsure how to fix an airlock, it’s best to call a professional plumber for assistance.

How can I tell if my boiler has an airlock?

Symptoms of an airlock in a boiler can include a lack of heating or hot water, strange noises coming from the pipes or boiler, or low water pressure. It is hard to know exactly if it is an airlock that is the issue without a full diagnostic.

What should I do if I suspect an airlock in my boiler?

One possible solution is to bleed the radiators, which involves releasing any trapped air from the system. This can be done by turning off the heating system and using a radiator key to open the valve at the top of the radiator. Another solution is to contact a qualified heating engineer who can diagnose and fix the issue.

Can an airlock cause damage to my boiler?

Yes, if left untreated, an airlock can cause damage to the boiler and other components of the heating system, such as the pump or pressure gauge.

How can I prevent airlocks in my boiler?

Regular maintenance of the heating system, including bleeding the radiators and checking the water pressure, can help to prevent airlocks from occurring. It’s also important to use high-quality water treatment chemicals to prevent the build-up of sediment and debris in the pipes.

Written by
James Elston
James Elston Director Of Boiler Central
Posted on: 16th May 2024
Topic: Boiler Advice

James Elston is our resident boiler replacement and heating expert here at Boiler Central. With over 20 years experience in the boiler installation industry, James ensures that he knows everything there is about our Gas Safe boiler installations, energy saving and home heating solutions. This can be from simply procuring the latest best combi boilers, to reviewing and ensuring that Boiler Central maintains the highest standards across our boiler installation company.

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