Airlock: what is it & how to get rid of it

An airlock is the result of air trapped in your plumbing system. It typically results in gurgling noises in pipes and sputtering at the taps. In some cases, an airlock can stop the flow of water altogether. Airlocks can also affect central heating systems and stop radiators from heating up properly.

The most effective way to get rid of them is to use pressurised water to push them out of the system.

Airlock explained

Airlocks in mains pressure plumbing systems are very rare. That’s because the pressure of the mains is almost always strong enough to displace any air. Most airlocks occur on the low-pressure side of a plumbing system, i.e., on things supplied by the cold water storage cistern. Your hot water cylinder and most probably your bathroom toilet and cold taps are fed by the storage cistern. Your kitchen cold tap is unaffected because it’s supplied by the mains.

Airlocks can also affect central heating systems. An obvious example of this is if your radiator is hot at the bottom but cold at the top. This is due to air stuck inside. You can usually get rid of this air by bleeding the radiators.

However, not all airlocks are bad. A primatic hot water cylinder uses an airlock to separate the hot water for the taps from the hot water for the radiators.

How to get rid of an airlock

The most effective way to get rid of an airlock in the pipework is to use mains pressure water to push it out the system.

You can achieve this by connecting the outlet which has an airlock to a tap with mains pressure water, usually the kitchen cold tap. You can do this with a length of garden hose and a couple of tap connectors.

Of course, it doesn’t have to be the kitchen cold tap. If you’re trying to fix an airlock in the pipe for your bathroom sink’s hot tap, and the cold tap is mains fed, then you can simply use that one.

Once you’ve connected the two taps together, open the tap with an airlock first, then open the mains tap. Let it run for 20-30 seconds, then turn the mains tap off first and then the problem tap. Remove the hose, and the airlock should hopefully have shifted.

If’s on a mixer tap

This method becomes a little more complicated if the hot and cold taps aren’t separate and unfortunately won’t work if there are non-return valves on the pipework or inside the tap itself.

If the cold side is fed from the mains, use the palm of your hand to form a watertight seal over the outlet of the tap, squeezing as tightly as you can. Next, open the tap in the mixed position, so that both hot and cold outlets are open. Turn the tap off after 20-30 seconds, and the airlock should hopefully be gone.