Clearing an Airlock in Water Pipes: How To Do It Yourself

Airlocks in your water pipes can cause problems.

Fortunately, there are simple ways to fix this yourself.

Important disclaimer: Consider calling a professional first!

It’s always best to call out a professional for water pipe problems.

They will diagnose the problem correctly, which will reduce the chances of damage.

However, if you need - or want to - clear an airlock, the below steps will guide you.

Diagnosing the problem

Airlocks in water pipes can cause several issues, including: 

• Banging pipes. This is caused by water bouncing off air bubbles blocking its path in pipes.
• Erratic flows from taps. Often weak and ‘spluttering’, sometimes suddenly spraying water.
• Weak cold water pressure. This often affects water fed from a cold water storage tank rather than directly from the mains. It can cause toilet cisterns to refill slowly and bath taps to run weakly.
• Noisy shower pump. Air that gets into a power shower’s pump can cause it to overheat and break.

If you aren’t experiencing any of these issues, an airlock is likely not your problem.

Look beyond the pipes: Other issues to consider

Air bubbles can also get into radiators.

If it's cold weather, you should also consider whether you need to thaw your pipes.

Boilers are sophisticated pieces of machinery with many components. 

If you aren’t certain there’s an airlock in your water pipes, it’s worth considering whether basic boiler problems are causing your issues.

(And if you live in the UK and have boiler cover with YourRepair, then we will get the job done for you!)

Option A: The Quick Fix - The Cross-Over Flush 

This is a classic (/old-school) DIY plumbing maneuver for clearing airlocks. It’s best for fixing issues with a single, stubborn tap.

Equipment needed

• A hose pipe at least 1 metre long
• Strong gaffer/duct tape or (preferably) two hose clamps (Jubilee clips)

Steps to take

Step 1: Check everything is on

Make sure your water is on/active. Ensure your main water stopcock is fully open and the small valves on the pipes under your sink are turned to the "on" position (the lever should line up with the pipe). 

Step 2: Connect taps 

Choose a sink with separate hot and cold taps. Connect the hot tap to the cold one using the hose pipe.

Step 3: Create a strong hose seal 

Secure the open ends of the hose tightly over the taps to ensure the water pressure won't blow the hose off. 

Hose clamps will give the strongest seal. If you are using duct tape, tie it tightly several times around. 

Step 4: Turn on the hot water 

Turn on the hot water tap (the one you have the hose tied to) fully.

Step 5: Turn on the cold tap (briefly) 

With the hot tap still running, slowly turn on the cold tap. Let it run (as the hot water tap is still running) for 30 - 60 seconds.

Listen closely for the sound of air being released. It should sound like a gurgling or sudden ‘burping’ noise.

Step 6: Turn off the taps

First, turn the cold (mains) tap off first, then the hot tap. (If the cold tap, i.e., mains tap, is still running into the hose and you close the hot tap, the mains water pressure has nowhere to go. So, it could  blow the hose off the tap and create a mess!).

Step 7: Repeat or finish 

Remove the hose from the taps. Check if another hot water tap is working in another sink in the house. If the water is spluttering, go back to step one: You may need to repeat this process at least 5 times.

If your hot water is working after that, and there is no spluttering, the process has worked. If not, consider Option B.

Option B: The Drastic Measure - A System Reset 

This is a process for clearing the entire hot water system, i.e. when multiple taps are showing signs of an airlock. It should force out any air that’s trapped in your hot water system, allowing the hot water to flow out of your taps again. 

This is a riskier process than Option A. 

Before you start, turn off your boiler or immersion heater. Modern boilers use a "heat exchanger" to heat your water. 

If you turn the boiler on while air is still trapped inside, the metal can overheat instantly because there is no water to absorb the heat. This "dry-firing" can crack components or cause the boiler to shut down.

Step 1: Turn off your water supply 

Do this at the mains stopcock.

Step 2: Turn on every tap in the house 

Start at the top of your house and work your way downstairs.

Step 3: Let the water flow… 

Wait for the water to stop flowing out of the taps.

Step 4: Flush toilets

Now flush all the toilets until no water is left in their bowls or cisterns.

Step 5: Turn your taps almost off 

Adjust them until only a small amount of water can trickle out.

Step 6: Turn your water supply back on. 

Do it slowly! Doing it fast could create a 'water hammer' (a violent vibration that can loosen pipe joints). This is because a sudden rush of water into an empty system can hit air pockets.

Open the stopcock gradually to let the pressure build up gently.

Step 7: Turn on all taps halfway

Open each tap to a halfway point. You will likely hear a lot of noise as you do this, including: 

• Hissing
• Gurgling
• Spluttering
• Creaking. 

This is the air being pushed out by the new wall of water.

Keep the taps running until the flow is steady and the above sounds have stopped. This ensures the air is fully flushed out of the water pipes and - crucially - out of your boiler's internal heat exchanger. 

Step 8: Fully open up all the taps. 

Once the flow is steady, open them all the way to clear any final small airlocks. When you are happy the water is flowing perfectly, you can turn the taps off and switch your boiler back on.

If this doesn’t work (and you have tried option A), you’ll need to contact a heating engineer to resolve the problem. 

It may be that debris  - rather than air - is blocking your pipes. In this case you will need to organise a powerflush.