Airlocks: What they are and how to fix them.

The brutal winter is coming to strike again, and it’s absolutely not the time where you want cold radiators or no water at all in your hot taps. These are the symptoms of an Airlock in your system.

So what’s happening when you get an airlock in a pipe? 

Water stops circulating in your system if air gets trapped in there – it stops radiators from being able to heat up and stops hot taps from running completely. In order to get the water flowing again, you need to release that air from the system. 

How to clear airlocks from your pipes.

We’re going to assume right here that you’re after a DIY fix, which is fine and it’s manageable if you know it’s an airlock. If you’re not sure what it is though, it’s best to call out an engineer to diagnose it. 

Method 1 – Duct Tape and Hose Pipes for treating airlocks

There’s two ways to do this for your hot water system. The first is quicker but requires DIY style equipment, namely a bit of hosepipe and some duct tape. 

Once you know that your hot water system is affected by the airlock, you’ll need to make sure the hot water supply is turned on, so if you’re turned off your boiler trying to figure out the issue, turn that bad boy back on before you start. 

What you essentially need to do here, is pour cold water into your hot tap. You’ll do this by connecting the hose pipe to your cold water tap with the duct tape. Prepare for some leakage around the tape. 

Now tape the other end of the pipe to the hot water tap, again where the water usually comes out. 

Now open the hot water tap fully, you’ll probably (hopefully) find that no water is coming out, which should be the issue in the first place. When the hot tap is fully open, open the cold tap for 3 to 5 seconds, then turn it off. Run to another sink and run the hot water tap for 30 seconds, or until hot water comes out. 

After 30 seconds, try running the cold tap into the hot tap again for another 3 to 5 seconds before turning off the cold tap again. Run back to the other sink and run the hot tap again. 

Rinse and repeat until you get hot water again.

Treat Airlocks in your hot water system

Method 2 – Unleashing all taps to remove airlocks

If that hasn’t solved your airlock problem then you’ll need another method, which involves more back and forth.

Start by turning off your mains water supply. This is usually a tap under the sink, or potentially somewhere under the boiler but not part of it – typically near the floor. 

Turn on every tap in the house, begin with the top floor and work your way around to downstairs, then wait for the water to stop coming out. 

Next flush every toilet until they stop flushing. 

Now go back round and turn your taps so that they’re only slightly open – not loose but not tight, you want a small amount of water to be able to get through.

Turn the water supply back on, then go round each tap and open them to about half way. This should release any trapped air in the system, allowing the hot water to flow out again. 

If neither method has worked, it’s time to call an engineer out to help diagnose the problem.

What about airlocks in central heating systems?   

Cold spots on your radiators are a strong indication of an airlock in pipes, particularly at the tops of the radiators or the bottoms. This is because the air acts as a blockage in the system, stopping the hot water from circulating around the radiator effectively. Before long, you’ll find yourself turning up the heating and putting additional strain on your boiler.

Fortunately, clearing this trapped air is simply a case of bleeding the radiators. You can do this safely yourself and all you need is:

Radiator key which can be picked up from most DIY shops for a few quid

Dry cloth (or towel)

A container to catch water

Bleeding the radiators

Step 1: Start by turning off the central heating and wait for it to cool all the way down, there’s going to be water coming out of the radiators and you don’t want it to be boiling.

Step 2: Use the radiator key to turn the bleed valve at the top of the radiator in an anti-clockwise direction. Place the container underneath to catch any water that may come out of the radiator.

Step 3: As you turn, you’ll hear a hissing sound which is the air escaping. Once this sound ends water will trickle out so turn the valve clockwise to lock the valve. Avoid doing this too tightly.

Follow this process for all of the radiators around your property. Once you’ve finished, check the pressure gauge on your boiler (it should be around 1.5) and make sure there’s no sign of leaking. If your boiler’s dropped in pressure as a result of letting air out of the system then you can read our guide on pressurising your boiler here.

What else could be the issue?

Cold radiators can also be caused by a build-up of sludge in the heating system, this will result in frequent need for bleeding radiators. To clear this, you will need to arrange for a qualified heating engineer to perform a powerflush.

Powerflushing a heating system takes many hours, sometimes days. It involves using a high pressure machine to force chemicals around your system, which then start to break down the sludge, bacterial growth and debris. Think of it as if a firefighter blasted your oven clean with a hose, but a lot less messier.

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At Borthwick Heating we work with the UK Government to install free boilers to eligible UK Homeowners. To check if you qualify click the button below.

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