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To remove an airlock from water pipes, connect the affected tap to a mains-fed tap using a hose. Briefly turn on the mains tap so the water pressure pushes the trapped air out of the pipe. You can also open several taps to release trapped air. If the airlock persists or keeps returning, contact a qualified plumber.
An airlock in your water pipes can turn a perfectly ordinary morning into a small plumbing puzzle. You turn on a tap expecting a steady stream, but instead you get spluttering, irregular flow or perhaps no water at all.
Airlocks happen when a pocket of air becomes trapped inside the pipework. The trapped air can restrict or completely interrupt the movement of water, particularly in gravity-fed plumbing systems where the available water pressure is relatively low.
Fortunately, many minor airlocks can be removed without dismantling the plumbing system. The important part is identifying whether trapped air is actually causing the problem and then choosing a suitable method to clear it.
This guide explains how to remove an airlock from water pipes, how to recognise the warning signs, what causes trapped air, and how to reduce the likelihood of the problem returning.
A plumbing airlock is a pocket of trapped air inside a water pipe that prevents or restricts normal water flow.
Water usually travels through domestic pipework under mains pressure or pressure created by a gravity-fed system. When air enters the pipework and becomes trapped at a high point or awkward section of the system, it can interfere with this movement.
The result may be weak water pressure, spluttering taps or a complete loss of flow from a particular outlet.
Airlocks are particularly associated with traditional gravity-fed plumbing systems, although unusual water flow and trapped air can occur in other systems too.
The air itself is not normally the real concern. The problem is the disruption it creates within the water supply.
Before attempting to clear an airlock, make sure the symptoms actually fit the problem. Several plumbing faults can produce similar signs.
Typical symptoms include:
If every tap in the property has suddenly stopped working, the problem may be with the incoming mains supply rather than an airlock.
Similarly, consistently low pressure throughout the property could indicate another plumbing issue.
Air normally becomes trapped when the water supply has been interrupted or the plumbing system has been drained and subsequently refilled.
Understanding the cause is useful because an airlock that repeatedly returns may indicate a wider issue.
If the main water supply has recently been switched off for maintenance or repairs, air can enter the pipes while the system is empty or partially drained.
When the supply is restored, some of this air may remain trapped.
Replacing taps, changing pipework, installing a new bathroom fixture or carrying out other plumbing work can introduce air into the system.
Most trapped air clears naturally once the water begins circulating again, but sometimes an air pocket remains.
Some traditional British plumbing systems use a cold water storage cistern, commonly located in the loft.
If the cistern runs unusually low or empties, air may enter the pipes supplying certain outlets.
The layout of the pipework can occasionally make airlocks more likely. High points, unusual bends or sections where air can accumulate may allow pockets of air to remain trapped.
Draining down a plumbing system for maintenance creates plenty of opportunity for air to enter the pipework.
If the system is refilled too quickly or air is unable to escape properly, an airlock may develop.
There are several ways to remove trapped air. The best approach depends on your plumbing system, the affected outlet and how severe the blockage is.
Before starting, remember that you are working with pressurised water. Avoid forcing excessive pressure into pipework, and do not dismantle plumbing components unless you know what you are doing.
One traditional way of clearing an airlock involves using mains water pressure to push the trapped air back through the affected pipe.
This method is commonly associated with mixer taps or separate hot and cold taps that can safely be connected with a suitable hose.
First, establish which tap or water supply has poor or no flow.
For example, the cold tap may work normally while the hot tap produces almost nothing. That difference can help identify which side of the plumbing system contains the suspected airlock.
In many UK homes, the kitchen cold tap is supplied directly from the mains, although plumbing arrangements vary.
You need a reliable source of mains pressure for this method.
Use a suitable, secure hose to connect the working mains-fed tap to the affected tap.
Make sure the connection is tight enough to prevent the hose from coming loose when water pressure is applied.
Keep towels nearby in case of leaks or splashing.
Open the affected tap first.
This provides a route through the affected pipework.
Slowly open the working mains-fed tap.
The increased pressure can push water backwards through the affected pipe and dislodge the trapped air.
Only apply the pressure briefly rather than leaving the taps connected for an extended period.
Close the taps carefully and remove the hose.
Then test the previously affected tap normally.
If the flow returns steadily, the trapped air has probably been cleared.
If the problem remains, do not repeatedly increase the pressure in an attempt to force it out. Another issue may be responsible.
Some mixer taps provide another way of applying pressure to the affected supply.
If one side has strong mains pressure and the other appears airlocked, temporarily blocking the mixer outlet while opening both supplies may encourage water to move backwards through the affected pipe.
This needs to be done carefully because tap designs and plumbing configurations differ.
Do not use excessive force to block an outlet, and stop if water begins leaking around fittings or connections.
A flexible shower hose can sometimes help where the affected plumbing arrangement allows a working supply to be connected safely to the airlocked side.
The principle is similar to the tap-and-hose method.
Water pressure from a working supply is temporarily directed towards the affected pipe to encourage the trapped air to move.
Make sure the hose and connections are secure before applying pressure. Shower fittings are not designed for every type of reverse-pressure procedure, so avoid improvising connections that could come loose.
A mild airlock may clear without additional pressure.
Try opening the affected tap fully and allowing it to run for several minutes. If the water begins spluttering, that can indicate air is moving through the pipe.
You may also open other relevant taps in the property to help release trapped air.
Do not leave running taps unattended.
If the flow gradually changes from irregular bursts to a steady stream, the air may have successfully escaped.
For a persistent airlock, draining and carefully refilling the relevant part of the plumbing system may help.
This approach is more involved and should only be attempted if you understand your property’s plumbing arrangement.
A general process may involve:
The exact procedure varies considerably between properties and plumbing systems. If you are unsure which valves or supplies control the system, calling a plumber is safer than experimenting.
If you suspect an airlock, checking your taps systematically can help narrow down the problem.
Start with the cold kitchen tap because it is commonly connected directly to the mains in UK properties. Then test other cold taps, followed by hot taps and showers.
Pay attention to which outlets work normally and which do not.
For example, if the cold water works throughout the property but one hot tap has stopped flowing, the problem is likely to be localised to the hot water side rather than the incoming mains supply.
If neither hot nor cold water works anywhere, investigate whether there is an external supply interruption or closed stopcock before assuming an airlock.
Hot water airlocks are particularly common in older gravity-fed systems.
You may notice that the cold tap works perfectly while the hot tap barely produces water. Sometimes the hot tap will cough and splutter before the flow stops again.
Using controlled mains pressure to dislodge the trapped air can sometimes resolve the problem.
However, you should first understand what type of hot water system you have.
Modern pressurised and unvented systems operate differently from traditional gravity-fed arrangements. Techniques suitable for one plumbing system may not be appropriate for another.
If the problem affects cold water, determine whether the affected outlet is mains-fed or supplied from a storage cistern.
A single poorly flowing cold tap could have a local issue, while multiple affected outlets may point towards a supply or storage problem.
Check whether:
These checks can help distinguish an airlock from a different fault.
An airlock and low water pressure can look surprisingly similar, but they are not the same problem.
An airlock usually affects a particular pipe, tap or section of the system. It may appear suddenly and can cause spluttering, interrupted flow or complete loss of water.
Low pressure tends to produce consistently weak flow and may affect several outlets.
A partially closed valve, blocked filter, damaged pipe, faulty tap cartridge or supply problem can also reduce water flow.
If the water has always been weak rather than suddenly becoming weak, trapped air may not be the main culprit.
A simple plumbing problem can become a more expensive one if excessive force or pressure is used.
More pressure is not automatically better.
Excessive pressure can place unnecessary strain on fittings, flexible hoses, taps and older pipework.
Use controlled pressure and stop if anything appears abnormal.
A blocked tap aerator, faulty valve, closed stopcock, damaged pipe or external supply issue can produce similar symptoms.
Diagnosis comes before cure.
A hose can loosen when pressure is applied.
Stay beside the connection and be ready to shut the water off immediately.
Unscrewing fittings may look straightforward until several litres of water decide to explore your kitchen floor.
If clearing the air requires dismantling pipes, valves or hot water components, professional assistance is usually the sensible option.
Ignoring a Recurring Airlock
An occasional airlock after maintenance is one thing. An airlock that repeatedly returns deserves further investigation.
There may be an issue with the pipe layout, storage system, water level or another component.
You cannot prevent every air pocket, particularly when plumbing work requires the system to be drained. However, careful maintenance can reduce the risk.
After plumbing work, restore the water supply gradually.
Allowing water to refill the system in a controlled manner can make it easier for displaced air to escape through open outlets.
After the system has been drained, taps can be opened strategically while water is restored to help trapped air escape.
Avoid immediately opening every outlet at full flow.
If your home uses a cold water storage cistern, ensure it is functioning correctly and maintaining an appropriate water level.
A faulty float valve or another issue that allows the cistern to run dry could introduce air into the supply.
If one section of your plumbing repeatedly develops airlocks, the pipework may require professional assessment.
The solution should address the cause rather than turning airlock removal into an unwanted household ritual.
Basic airlock-clearing techniques may be suitable for simple domestic plumbing problems, but there are situations where professional assistance is the better choice.
Consider calling a qualified plumber when:
A plumber can determine whether trapped air is genuinely responsible or whether the symptoms are being caused by a blockage, valve fault, pressure problem or another plumbing defect.
For homeowners and property managers dealing with plumbing or general property maintenance concerns, Peak Performance Maintenance LTD. can provide professional support when a problem requires more than a straightforward DIY check.
A simple pocket of trapped air does not necessarily mean your pipes are damaged.
However, abnormal pressure changes, persistent flow problems or attempts to clear an airlock using excessive pressure can potentially place stress on plumbing components.
This is particularly relevant in older systems where joints, valves and fittings may already be worn.
Persistent banging or unusual noises should therefore not simply be ignored.
The safest approach is to clear minor trapped air carefully and investigate any recurring symptoms.
A straightforward airlock can sometimes be cleared within a few minutes.
If a hose method works immediately, normal water flow may return quickly. More stubborn airlocks can take longer, particularly if the affected pipework is difficult to identify.
If repeated attempts do not improve the flow, stop treating the problem as a confirmed airlock.
Continuing to force water through the system could create unnecessary risk when the real problem may be a blockage, faulty valve or another plumbing issue.
Learning how to remove an airlock from water pipes can save considerable frustration when a tap suddenly starts spluttering or stops producing water.
The first step is diagnosis. Check whether other taps work, determine whether the affected outlet is hot or cold, and consider whether the problem started after plumbing work or a temporary interruption to the water supply.
For a straightforward airlock, controlled mains pressure through a securely connected hose may help dislodge trapped air. Mild cases may also clear by running the affected taps, while persistent problems can sometimes require the system to be drained and refilled correctly.
The key word is controlled. Avoid excessive pressure, improvised plumbing connections or dismantling components you are unfamiliar with.
If an airlock refuses to clear, keeps returning or is accompanied by leaks, severe noises or widespread loss of water, professional diagnosis is the safest next step.
A common method is to use a secure hose to connect an affected tap to a working mains-fed tap. Briefly applying mains water pressure may push the trapped air out of the affected pipe. The exact method depends on the plumbing system.
A small amount of trapped air may sometimes clear naturally when water is allowed to flow through the affected outlet. A larger air pocket can remain trapped and may require controlled pressure or another suitable method to remove it.
Common signs include spluttering taps, intermittent water flow, unusual gurgling noises and one or more outlets suddenly producing little or no water. Similar symptoms can have other causes, so an airlock should not automatically be assumed.
Air may have entered the pipework while the water supply was off. When the system was refilled, an air pocket could have become trapped. However, also check that the stopcock and other relevant valves have been reopened correctly.
Repeated airlocks may indicate an underlying problem such as an unsuitable pipe layout, a storage cistern running low, recurring supply interruptions or another plumbing fault. If the problem keeps returning, the system should be professionally inspected.
