What Causes Banging Noises in Plumbing Pipework

24 Hours 7 Days a Week emergency repair call out service 0800 246 1375


  • Introduction
  • Summary
  • What Causes Banging Noises in Plumbing Pipework?
    • Normal Starting up Process
    • Airlocks
      • Removing Airlocks From Radiators
      • Removing an Airlock From the Central Heating System
    • Loose Fittings
    • Copper Pipes
    • Water Hammer
    • High Water Pressure
    • Blockages and Sludge Build up
  • Conclusion


We have probably all been woken up in the middle of the night in a slightly perturbed sate, wondering why it sounds like there is a giant banging on your door! Once you have gathered your senses you realise that this cacophony is in fact coming from your water pipes and things are not quite that bad as initially imagined. Noisy pipes are a common occurrence, especially in older homes. Whilst strange noises coming from your pipes can be annoying, they can also be worrying. Nobody wants to experience plumbing problems, the prospect of potential issues causes you to imagine thoughts of all sorts of nightmare scenarios, from emergency leaks to expensive replacements.   This article will explain what causes banging noises in plumbing pipework and briefly explains the measures that can be taken to resolve the most common causes. Knowing how to perform some relatively simple maintenance on your central heating system is important knowledge, and if you are confident doing so then you can not only ensure that your property is well heated and maintained but can also save money in several ways. Obviously if you are doing this yourself then you are saving yourself significant costs on employing professional tradesmen but you will also have a far more efficient heating system which will not only save you money on your regular bills but will also contribute to reducing environmental pressures. The good news is that this issue can be easily resolved in the majority of causes and is usually neither dangerous or particularly damaging to your plumbing system. Don’t be afraid of these procedures, like any process around the home if you follow the steps in a logical manner then the resolution of these issues should be relatively simple. However, as with many projects involving water or electricity if you are not totally confident then do not hesitate to employ the services of a qualified professional. It can sometimes be useful to follow them around and watch what they are doing so you will know for next time!

What Causes Banging Noises in Plumbing Pipework?

There are numerous things that can cause banging noises in plumbing pipework. We will examine the most common and offer some potential solution as well as explaining the causes.

Normal Starting up Process

Sometimes the noises that you hear are just a natural occurrence of your system starting up as everything begins to heat up. This is definitely something to consider when wondering what causes banging noises in plumbing pipework. Every component in your plumbing system including pipes and radiators will expand as they begin to heat up. Bearing in mind that a normal heating system will take between ten and thirty minutes to completely heat up. This means that if your hearing noises such as banging, knocking and tapping that are only present for this period then it is extremely likely that these noises are all part of the natural start up process of your heating system. You may also hear these noises when the heating goes off as the exact opposite is happening, except in this instance your pipes and radiators will be contracting as opposed to expanding. This issue can be resolved if you can identify specific locations where the noise is coming from. Once this has been identified then the pipes can potentially be moved or re-routed to avoid touching any surrounding structures such as floorboards.


When looking at what causes banging noises in plumbing pipework airlocks are a very common cause. If the sound is a harsh banging or a clunking noise then it is extremely likely that there is an airlock somewhere in your system. Usually in the pipework, pump or the radiators. Airlocks in your radiators can occur when air / vapour becomes trapped in your central heating system and this subsequently prevents hot water from moving into the radiator, leaving them cold. In your property your central heating system is responsible for distributing hot water throughout the building into the radiators, which will then heat your home or business. Sometimes however this process can create excess water vapour and as this has a lower density than water it will rise to the highest point in your system and create what is known as an airlock. When your central heating system is initially filled with water, this water will contain dissolved air that could constitute up to one sixth of the volume, if this is not released after a few days then this too could cause airlock issues. It is worth mentioning that sometimes the ‘air’ that is causing these problems may not be air at all. Sometimes chemical corrosion can form gases as part of the corrosion process if your system has not had any corrosion inhibitor chemicals added. These airlocks can be responsible for all sorts of problems within your central heating system from a lack of heat coming from individual radiators to a total loss of heating throughout your property. You may also experience an airlock in the heating system itself as opposed to in individual radiators, which could potentially result in a total lack of all heating. This can sometimes happen when you have had your system refilled in the wrong order, usually caused by filling downstairs radiators when the upstairs ones haven’t been closed off. The piping (flow and return) for your central heating system can sometimes run vertically on walls, or in cupboards and the flow in these pipes can go upwards or downwards. This is not an issue when the normal flow direction is upwards as the air will normally be flushed out of the vertical pipe. However, when the water flows downwards the air cannot be flushed quite as easily. Combine this and a lower pressure from the pump and you have the perfect situation for airlocks to form, leading to some, or all of your radiators failing to heat up, depending on how many radiators the affected pipe serves.

Removing Airlocks From Radiators

The good news is that this can be quite easily remedied with just a bowl, some towels and a radiator key or screwdriver. Once you have these tools to hand then the following steps should resolve any issues that are caused by air being present in the radiators.

  • Ensure that all radiator thermostats are set to full and run the heating system for at least 10-15 minutes to give the radiators a chance to warm up
  • Try and identify which radiators require bleeding, these can be identified by those that are producing gurgling noises or have cold spots at the top whilst remaining hot at the bottom
  • Ensure that your central heating is turned off until the radiators have cooled down. Allow between 30 minutes and an hour for this
  • If your home has more than one floor then you should begin bleeding the downstairs radiators first.  It’s also advisable to start with the radiator which is furthest away from the boiler.  Once you’ve bled all the downstairs radiators you move on to the upstairs, again beginning with the radiator which is furthest from the boiler.
  • For each affected radiator being bled, position the towels on the floor below the radiator to catch any excess water that may escape and to protect your floor from staining
  • Identify the radiator bleed valve, this is normally found at the top of the radiator and is a round hole with a square inside, double check that your towels are directly below this valve as this is where any excess water will drain to
  • Be aware that the radiators will be hot, so please take extra care at this point as there is a danger of burning yourself
  • Using the radiator bleed key turn the square slot anti clockwise, you do not need to turn this more than half a turn at this point. Having done this you should hear a hissing sound, this is entirely normal, and is a sign that the trapped air is escaping the radiator
  • Keep the radiator key in place until you start to see or feel a little water coming out, let the water splutter and wait until there is a constant stream, this will ensure that you have released all of the trapped air. At this point take note of the colour of the water, if the water is black then this could be indicative of a dirt build up and a power flush may also be required, this will usually require the additional services of a qualified tradesman
  • Re tighten the bleed valve by turning it clockwise, this will reseal the radiator. Take a few extra seconds to ensure that there is no more water escaping the radiator at this point and be careful not to overtighten
  • Work your way around your property repeating this process for all of the radiators that you had previously identified as having an issue
  • Turn your heating back on and repeat the checking of the problematic radiators, if this has resolved the issues then sit back and reflect on a job well done. If the issues still remain then you may need to seek further professional advice

Removing an Airlock From the Central Heating System

If your issue is with an airlock in the heating system itself then there are several other methods that could help to resolve this.

  • The first problem may be a lack of pressure from the pump, these pumps usually have a variable setting for pressure so try to turn up the pressure which may force the airlock out of the system

If the adjustment of the pump fails to resolve the issue then there may be a faulty radiator or a locked pipe. This can be identified by following these steps:

  • Take a note, or a quick picture, of the setting on the boiler thermostat and set this to the minimum. If you have an older boiler, which allows you to switch the thermostat off completely and leave the pump running then you can switch the thermostat off completely
  • Ensure that the pump speed is set to the highest setting possible
  • If your boiler heats both a water tank and the heating then turn the heating setting to ‘Off’, this should now ensure that you will have the maximum pressure running to your radiators
  • Turn off all radiators except for the one closest to the boiler, this will reduce the risk of your boiler overheating.
  • Turn on the next radiator, whilst leaving the previous one on, once you have confirmed that the radiator is working you can turn off the previous radiator
  • You may hear a gurgle of air as your radiator clears and the radiator may suddenly start to get hot, excellent work!!
  • Repeat this exercise until all of the other radiators are returned back to their original settings and are functioning correctly. You may have to repeat this process several times with individual radiators however this will usually resolve the issues and leave your radiators ‘balanced’
  • Make sure that you return the boiler thermostat to its original setting, turn the hot water setting back on if you disabled this in earlier steps and finally set the pump back to its original speed

If at this point you have still not resolved the issue then it is probably time to seek additional professional advice

Loose Fittings

Occasionally it is sometimes the most obvious thing that is causing the problem. If you are trying to ascertain what causes banging noises in plumbing pipework then one of the culprits may be something as simple as loose fittings. If your pipes are clunking, vibrating or rattling them it could just be a matter of your pipes mot being fitted correctly. As water moves around your property there is a resultant build up of pressure and friction and if your pipes are not correctly fitted then the vibrations and rattles will soon present themselves. It may well be that these pipes were not fitted correctly in the first instance or that as time has progressed they have become loose. No matter the cause these issues will need to be addressed. Occasionally you may notice a humming sound or a constant vibrating, this is nearly always caused when a pipe has either not been secured properly in the beginning, or have escaped the pipe clips. Relocating the pipes in the clips can provide an instant fix in these situations. If you can identify the localised source of this noise, and the pipework is either exposed, or accessible then you can attempt to tighten the visible bolts or identify, and potentially replace any worn out fixtures and fittings. If however, you cannot reach or identify the exact location of the noise then it may be time to call for professional help.

Copper Pipes

Something else to consider when looking at what causes banging noises in plumbing pipework is the copper pipes themselves. The majority of houses will have their pipework in the constructed from copper. Because copper is a durable, malleable metal it has been used to replace older systems constructed in either lead or steel and is the first choice when installing new systems. For all of its benefits however copper does contract and expand with changing temperatures. If you are experiencing noisy pipes and this tends to occur only after you have used hot water then the likely culprit is expanding copper piping. This is caused when the warmed, and subsequently expanded pipe rubs against other hardware in the home, such as joints, brackets and supports. This issue should not overly concern you as your copper piping is designed to handle this expansion however there are some methods of noise management available if the noise becomes too much of an issue. This problem can be resolved by the addition of foam rubber to avoid friction against other surfaces or your hot water temperature can be reduced to reduce the amount of expansion.

Water Hammer

When looking at what causes banging noises in plumbing pipework airlocks you may have what is referred to as ‘water hammer’. Banging and thudding noises within your plumbing system are probably the most alarming noises that your system will produce. In some instances these can do have the potential to cause damage. A water hammer will occur if you begin to have failures in the inbuilt protection systems within your plumbing system. Most taps have air chambers installed nearby to prevent rushing water impacting valves when taps are turned off. Over a period of time however, this air is replaced by water which subsequently reduces the stopping power of the air chambers. This chain of events leads to water crashing into these valves which produces that thudding noise. To try and fix this issue you can follow the below step:

  • Turn off the water mains supply
  • Turn on all of the taps on the top floor of your property, ensuring that no plugs are left in
  • Work downwards until all of the taps in your property
  • Allow all of the water to drain from your system
  • Once water stops coming out of your taps (the system has been drained), turn the water back on at the mains
  • Leave all of taps until water begins flowing again
  • Turn off all of your taps

Your air chambers should now be replenished with enough air to absorb the shocks and stop the thudding sound from reoccurring. If the above steps do not resolve the issue then you should request help from a qualified plumber.

High Water Pressure

This is another cause of noisy pipes that can potentially have serious consequences if not handled properly. However, do not panic as it can also have a very simple solution. These noises will generally occur if the water pressure is too high, purely because it is being forced through pipework far too quickly and is crashing around. Normally domestic water pressure should be between 1 to 1.5 bar. If you are running at a pressure any higher than this your pipes and appliances will be overworked and could become damaged. Most modern water systems now have a pressure meter and regulator installed. Simply locate this pressure meter, and adjust the pressure accordingly. You may need to consult the manual at this point but this is usually a simple exercise.

Blockages and Sludge Build Up

Over a period of time your pipework will obviously suffers some wear and tear. This is especially prevalent in hard water areas. Your central heating system will also create sludge that can circulate throughout your pipes and heating system. This sludge is usually a combination of limescale and rust from inside the pipes breaking off. If this occurs, then solid particulates will begin to travel throughout your pipework. This issue is usually quite easy to identify as the sound is quite easily distinguishable, more of a rattling and a clinking as the solid particles hit the pipes. If you have identified this issue, then this is one of the few situations that we suggest that you refer straight to a specialist rather than attempting to flush and clean your pipes yourself. There are several solutions that the heating engineer can implement to resolve this issue, and these are as follows:

  • Treat your system with a sludge inhibitor that will break down sludge and limescale
  • Fit a scale reducer in hard water areas to prevent future limescale build up
  • Perform a flush of your system to remove sludge and limescale
  • Fit a magnetic boiler filter that will attract and capture central heating sludge


If you have got this far then you should have more awareness of what causes banging noises in plumbing pipework, and also any remedial steps that you can take yourself to resolve these issues.   The resolutions described in this article can all be performed with minimal DIY ability. However, as ever when dealing with water, gas or electricity if you are at all unsure then please consult a qualified professional before attempting to undertake any of these steps.   Now you know what causes banging noises in plumbing pipework you should be able to rest easier when you are awoken by unexpected noises in the middle of the night!