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What Causes A Noisy Central Heating System?

A noisy central heating system can be caused by several things, many of which you can fix up yourself.

In this guide. I’m going to cover a lot of different sounds that your boiler, pipework, radiators or central heating system may be making and help you to cure a range of noisy central heating problems.

Man in a purple shirt putting his finger sin his earsSo, if your heating is –

  • Gurgling
  • Tapping
  • Humming
  • Creaking
  • Clicking
  • Knocking

– let’s dive right in and cure that noisy central heating!

What’s That Awful Noise?

A cross section layout of a gas central heating system in standard house

Most of the components that make up your central heating system are made from metal, and metal – as you probably already know – will expand and contract as it heats up and cools down.

So it may be that the sounds you’re hearing your central heating make are just being caused by that natural process.

Because pipework creaks and groans as it expands and contracts, it can be something that you get used to – but if your central heating is making strange noises, it’s best not to ignore it.

More serious causes of annoying and loud central heating should be fully investigated and fixed by a qualified plumber, with the worst case scenario being that you have to part with a little bit of money to get it sorted.

But here at BestHeating, we like to give you the tools to fix things for yourself – so this guide is designed to help you identify the most common causes of noisy heating systems to help you to solve the problems without having to splash the cash on expensive repair bills.

Do You Have A Noisy Boiler?

Gas engineer fixing a faulty boiler

Boilers often make gurgling noises, so most of the time it is perfectly normal to have a noisy boiler.

But, if you think your boiler is making louder, more unusual noise then it is best to check it out and make some adjustments.

Here are some things that you can try to stop your boiler making noise.

If you have a conventional system there’s a chance the small F&E heating tank (normally in the loft) might be dry and drawing air into the system. This will result in a noisy system before eventually coming to a complete stop. If you find the F&E tank is dry, check that the ball valve is not stuck in the lifted position. Simply move the arm up and down and that should start the flow of water back into the tank. If this doesn’t allow the water to come through then the ball valve may need replacing.

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How To Stop A Noisy Boiler

REMOVE LIMESCALE

If you have a noisy boiler – for example, if it sounds like a kettle boiling – it may be a sign that limescale has built up inside your boiler’s heat exchanger.

The limescale settles and restricts the water flow. So, the trapped water inside the heat exchanger gets too hot.

As the water starts to boil, steam and expand, the boiler makes a kettling noise similar to a whistling kettle. This quite common in older heating systems.

To remove this excess scale, a descaler can be added to your feed and expansion tank.

Once you’ve allowed it to make its way around the system, you should flush your central heating with clean water and add some radiator inhibitor, to help prevent corrosion.

Removing the limescale build-up will not only stop your boiler from making a noise, but it will also improve the lifespan and efficiency of your boiler by allowing water to pass through the system easier.

CHECK THE FLOW RATE

A noisy boiler could also be caused by a low water flow in the system. Modern gas boilers – and it’s important to know this – require a particular flow rate in order to operate properly.

Making sure this is correct will help you to diagnose the problem and stop your boiler gurgling.

You should be able to find the required flow rate in your boiler manual, or if you get really stuck you could contact the manufacturer and get them to provide the information to you.

REMOVE SLUDGE & DEBRIS

If your boiler is not regularly serviced, you may find that noise begins to happen more often when you turn it on or when you are using your hot water.

It may also be a good idea to install a Magna clean to help rid your system of sludge or debris; these are also good for reducing carbon emissions if fitted with an auto bleed valve.

How To Prevent A Noisy Boiler

So, now you know how to tackle a noisy boiler – but how can you prevent limescale building up to avoid your noisy boiler in the first place? The good news is this process is even easier than getting rid of it.

INSTALL A WATER SOFTENER

One way to prevent your boiler making noise is to protect it from hard water. You can install a water softener near your main water supply. This will swap the pesky hard water particles for safe sodium particles to prevent the future build-up of limescale.

GET AN ELECTROLYTIC SCALE REDUCER

You can also improve the quality of your water and reduce limescale build up with an electrolytic scale reducer. This is a cheaper alternative to a water softener but still very effective way to prevent an annoying noisy boiler.

Are Your Pipes Banging?

Pipework exposed under some floorboards

When you open the taps in your bathroom, do you hear a banging noise?

This is called ‘water hammering’ and can be caused by a number of things, from pipework not being secured properly under the floorboards to overheating or perhaps a little air in the system.

If you can hear your pipes making a thudding sound, the first thing you need to do is check the thermostat – either on your wall or your boiler.

To do this properly, turn your boiler off and allow the system to cool down. Once you’ve had it switched off for a while, turn your heating back on again and crank up the thermostat, like you mean it.

You should hear a click when you do this, but if you don’t, call a professional engineer to come and diagnose the problem.

One of the most common causes of banging pipework is that the pipes under the floor are not secured correctly. Copper pipes need to be properly secured in order to prevent them from rattling too much.

A simple solution, that should fix the problem of banging pipes, is to squash some felt around each pipe under your floorboards. Try and concentrate on every place where a pipe touches a joist or another pipe and wrap a little felt around it to create a snug fit.

If you’ve already had someone look into this for you and the problem still occurs, it may be worth your time investing in some plastic pipework, which is much more flexible and won’t make anywhere near as much noise as a copper alternative.

Why Is My Heating System Gurgling?

If you notice a gurgling sound like a kettle as it’s beginning to boil, often the actual cause of the noise is not the boiler but somewhere else in your heating system like the radiators or pipes. There are a few reasons why you might have a noisy radiator or noisy pipes.

PROBLEM – HOW TO FIX A NOISY RADIATOR

The most common cause of a noisy radiator when the heating comes on is air trapped inside your system. It’s important to fix this issue as soon as you realise it is there.

Apart from having a noisy radiator, another good way to check for trapped air is to feel the radiator. If it feels hot at the top but cold at the bottom, then there is trapped air inside.

Heat will have a difficult time reaching where it needs to be if air is preventing it from travelling to certain areas of your home – and if you get really unlucky, your boiler might not start at all and then you’ll really be in trouble. 

WHAT TO DO – BLEED YOUR RADIATORS

You can easily solve the problem of trapped air in your central heating system by bleeding the radiators – watch the video below to find out how.

Follow this same process for how to bleed radiators on a combi boiler.

And check out our How To Guide on Bleeding Radiators for some extra, in-depth help.

PROBLEM – NOISY PIPES

Another cause of gurgling in a heating system – particularly in colder weather – could be a frozen condensate pipe.

Colder weather can cause pipes to freeze, stopping water from circulating through the system.

WHAT TO DO – CHECK FOR FROZEN PIPES

image of a condensate pipe being warmed up with a jug of water

Your condensate pipe is normally a white overflow pipe that drains to the sewers outside of your home – and is usually found on an external wall outside of where your boiler is.

If your condensate pipe is frozen, it is normally at the most exposed external point – at the end of the pipework and near to the drain.

As in the image above, you can normally thaw a condensate pipe out entirely with a little warm water.

Using a suitable container – like a jug or a watering can – simply pour a little warm water onto the surface of the pipe to slowly thaw it out and remove the blockage.

Be sure NOT to use boiling water, as this can cause more harm than good, and once the contents of the pipe have fully drained and the blockage has been removed, restart your boiler.

PLEASE NOTE: Always follow the manufacturers guidelines to restarting your boiler, and if you’re unsure, give them a call.

Why Is My Central Heating Making A Tapping Noise?

A tapping – or gurgling sound like the one described above – could also be caused by a build-up of limescale within the pipes and radiators. If you suspect this is the problem, use a non-acidic cleaner to flush out the system when the heating is turned off.

The type of chemical cleaner you’ll need is dependent upon the age of your radiators and your boiler – discover how to choose the best one here.

Older central heating systems may need a much stronger solution than newer installations, so don’t just go and pick one off the shelf at the local plumber’s merchant – be sure to ask them which chemical cleaner is best for the age and condition of your system.

sludge in a cross section of pipework from a central heating system

Why Is My Central Heating Humming?

A humming sound coming from your heating could mean that the heating elements in your immersion heater are not functioning properly.

First, check that the thermostat is working correctly. If it is, turn your attention to the central heating pump; this may be set too fast and need slowing down.

If you think it’s necessary, turn the pressure down too, as too high a setting can result in pipe damage and clanging sounds.

If you have recently refilled your heating system, it could be that you’ve left the filling loop open slightly, or forgotten to disconnect it – as this is what the regulations state should be done. Or you might have knocked the valve accidentally and it may have become loose, allowing a constant flow of water into the system. Be sure to check that this isn’t the case.

You can reduce the pressure in your boiler by bleeding your radiators, check out this infographic for an easy guide, or by using the pressure relief valve in your boiler.

Why Is My Central Heating Making A Knocking Sound?

As water in the system heats up and flows through the pipes, it causes them to expand – and contract again once cooled.

If there’s insufficient room beneath the floorboards for this to happen, then noises will occur.

Check the position of the pipes and make any necessary adjustments if you find they are too close to the joists or floorboards – you can just use a saw and a chisel to make more room.

If the pipes have room to expand but are still making a noise, pack some light insulation around the pipe as that should help to limit movement and dull the sound.

Central Heating Pump Noise

boiler-pump

If you’ve exhausted all avenues above – and your radiators are still making noise – it’s very likely that the root of your problem is your central heating pump.

Noisy heating pumps are common in the winter because the heat pump goes into defrost mode. As the internal valves shift into winter mode, the heat pump can make a swooshing noise which is nothing to worry about.

However, a lot of central heating pump problems are the cause of boiler issues. If your hot water pump isn’t working correctly it could lead to a noisy boiler, leaks or even stop your radiators from working properly.

So, if you think there are unusual noises coming from your heating pump, here are a few things you could try:

1. Secure Your Central Heating Pump

A common cause of a noisy central heating pump is the vibration of the boiler unit itself. If you find that this is the case, your heating pump will need securing in place and you could install simple brackets to make it more secure.

For a quick fix, try placing something under the boiler like rubber pads to absorb the vibrations and stop the boiler making noise.

2. Adjust The Central Heating Pump Speed

You could also try turning down the central heating pump speed. It is quick and easy to adjust the pump speed. Especially if you have a newer model like a Grundfos central heating pump.

These pumps usually have 3 speed settings. Simply flick the switch on top of the boiler pump. 1 is the slowest pump speed and 3 is the fastest.

But just be aware that turning the pump speed down may lead to your radiators taking a long time to heat up. So if the problem persists, be sure to contact the professionals.

3. Bleed The Central Heating Pump
Just like noisy radiators, another central heating pump problem is caused by trapped air locks in the pump. To remove the air locks you will need to bleed your heating pump.

This is a similar job to bleeding a radiator. You should find the pump bleed screw on the side of the heating pump.

Turn the pump heat screw about half way and slowly let the air out. Be prepared for a bit of water leakage and keep a tea towel at hand.

4. Check The Heat Pump Fan
Does your heat pump make a loud clanking noise like metal banging together? Often the cause of this noise is the heat pump fan hitting something that it shouldn’t inside the unit.

To check if this is the case, make sure your boiler pump is switched off and check the fan blades. You may find that there is a loose component tapping the blades causing the heat pump to make noise.

Keep Calm & Carry On Heating

If your boiler is kettling, or your radiators are making loud noises, don’t panic.

To ensure safety and efficiency, all boilers and domestic water heaters come with built-in safety devices:

Safety Valves
If the internal boiler pressure gets too high, the safety valve automatically releases the pressure to stop the system from exploding.

Low-Water Fuel Cut-Off
If the boiler water drops below a safe level, this device will shut off the fuel or heat source. So the boiler will automatically shut down. This prevents the boiler from overheating.

Protect Your Safety Devices
Even your safety devices need a little protection to ensure they operate properly. Such issues like corrosion, restricted water flow and build-up of sludge and scale can interfere with your boiler safety devices.

So, make sure to follow the steps that we have mentioned to remove and prevent limescale. Your boiler operator should always check that the safety devices are working correctly when your boiler is being serviced.

Good Luck Curing Your Noisy Central Heating!

There’s usually a simple solution to the noise coming from your boiler or radiators, but if in doubt, give a local engineer a call and ask for some advice about your radiator or boiler installation.

If you’ve had some success with these tips and managed to cure your noisy central heating, don’t forget to leave a comment and tell us all about it – you never know, you might help someone else with their problem.

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