Boiler Making Noise? Here’s what to do

Boiler Making Noise

I was asked recently, “What should I do if my boiler is making noise?” Although this might seem like a plumber’s topic, there are definitely ways to approach it from a soundproofing perspective. That’s what I’m going to look at in this article. Here is a quick answer:

If a boiler is making noise, the first thing to do is confirm this is not a sign of a bigger problem. If not, then the best thing to do is apply some soundproofing solutions to the boiler to make it quieter and less noticeable.

In this article, I’ll look at the common issues that result in a boiler making noise, along with the best ways to tackle these problems. However, if you’re unsure about the source of noise, it’s still always best to contact a professional plumber.

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Reasons for a boiler making Noise

It’s perfectly normal for a boiler to make some noise because it has moving parts. If nothing else, the pump that pushes water around the heating system can be particularly loud, especially in older boilers.

Most of us get used to the normal noises a boiler makes, to the point where we often stop noticing it. Therefore if your boiler has started making noises that sound different, it could be a sign of a bigger problem.

That said, some people can even be put off by standard boiler noises. This is particularly true if you have an older model, as both the age of the parts and their design can result in them being much louder than newer models.

So the first thing to do if your boiler is making noise is to identify the source. This can be easy if your boiler displays an error message, which can be checked against the manual. However, it’s not always that simple to solve.

Many boiler noises can be described as whistling, humming, banging, clicking, tapping, or vibrating. Importantly, there are 7 fairly common causes of these issues, which are:

1. Low water pressure

Low water pressure can cause banging or hammering noises, both one-off and continuous. Low water pressure doesn’t always mean a leak in the system, as boilers can sometimes perform a pressure dump on their own.

If your system’s pressure is on the low side and the heating is then turned on, this spike in pressure can cause air to be pushed around the pipes, which is generally what causes the banging noises.

Your boiler should have a pressure gauge that’ll tell you whether the pressure is correct. If it’s low, you might have a leak in the system, in which case you need to locate and identify the problem.

If you can increase the flow rate in your boiler you should be able to solve the problem, if only temporarily. However, if it continues then the best thing to do is to call a plumber to fix it for you.

2. A build-up of sludge in the pipes

Sludge can build up in all boiler systems, particularly in older houses. It’s caused by breakdown inside the pipes, which is simply a result of water flowing through metal pipes, creating rust.

This sludge then travels around the heating system causing clicking and tapping noises. In a worst-case scenario, it’ll become lodged in the boiler and cause a blockage, much the same as how our arteries become clogged with cholesterol.

Fortunately, this is a fairly easy problem to fix. First, it’s worth trying to flush the system to remove all the sludge. This is much more successful if you throw some cleaner in there first, which helps to break down any larger or more solid parts.

Once you’ve done an initial flush, the best thing to do is install a boiler filter. A boiler filter is essentially a magnet and storage container attached to the pipework. It pulls out any metal as the heating water passes through it, keeping the system much cleaner.

3. Airlock in the pump

Much like any other appliance that deals with water, a boiler is prone to airlocks. An airlock is simply caused by – you guessed it – air in the pipes. This is particularly common on newly fitted boilers or when running hot water for an extended period.

An airlock in the boiler will cause banging, which might be once as the tap is turned off, or continuous if you’re running water for a long time.

Most boiler pumps will have a screw fitted that can be used to bleed the pump, much the same as you would with a radiator. However, if you can’t locate this easily then it might be best to call in a professional. They should get the problem solved fairly quickly.

4. Problem with the ignition

When you turn on a hot tap or the heating, your boiler should make some clicking sounds and then fire up. This is it lighting from the pilot light. However, if it taps and then does nothing, you could have a problem.

A series of clicking or tapping noises followed by not much will most likely mean your igniter is faulty or that there’s a problem with your gas supply. Either way, this is probably one of the more serious problems because it leads to the boiler simply not working.

The best thing to do here is to call out a plumber because this is a more technical problem than the others listed. More importantly, it could mean dealing directly with the gas supply, which is not something you should ever do.

5. Blocked heat exchanger

The heat exchanger is probably one of the most important parts of a boiler. After all, it’s the component that converts heat from gas into heated water. Therefore having a faulty one is problematic.

A boiler with a blocked heat exchanger will sound like it’s whistling or gurgling, which are never positive noises. It’s most likely caused by a build-up of limescale or sludge, but this might not always be the case.

This article offers more detail on how to diagnose the problem, and the first thing to try is a system flush like the one described above. However, it might be best to call in an engineer instead, as this is another potentially technical problem.

6. Limescale build-up

Much like sludge, your boiler system can become blocked by minerals in the water. This is a common problem in hard water areas, which is up to 85% of the USA.

These minerals attach to the pipes and boiler system, creating blockages. This can cause issues with the pressure and is characterized by hissing, tapping, and banging noises.

The best way to approach this issue is to flush the system with a limescale inhibitor and then fit a limescale reducer. However, it can take years to properly resolve the issue because mineral deposits are very hard to remove, particularly when you can’t see them.

If this seems like a challenge, call in an engineer because they’ll likely be very familiar with the issue if they work in a hard water area. Once the problem has been solved it’s best to regularly maintain your system to prevent it happening again.

7. Pump seizure

The boiler pump is probably one of the hardest working parts of the whole system. If it’s recently started making humming noises or is vibrating, then it’s most likely seized.

The first thing to do is to check how hot it is. A normal functioning pump will be warm but not hot. So if it’s warmer than you think it should be, it’s probably seized.

You should then try and diagnose the cause of the problem, which could be sludge caught in the pump. However, it’s not easy to do this without taking it apart.

If you call in a professional they’ll most likely suggest replacing the pump, which is often easier than trying to change a part. This isn’t particularly expensive either and will at least mean it’ll work for longer.

Is it even the boiler?

The other thing to consider is whether the noise originates in the boiler. Sound travels very well through pipes and so the problem could come from elsewhere.

The easiest way to check this is to stand near the boiler while it’s working. If it’s loudest at the boiler then it’s probably the cause. If the noise sounds louder when stood near the pipes then it’s coming from elsewhere.

How to make your boiler quieter

boiler sound reduction

Providing the noise your boiler is making isn’t a sign of a bigger problem, it’s worth trying to find ways to make it quieter. Luckily this is fairly easy with the wide range of soundproofing materials available.

Before going into how to reduce the noise your boiler makes, it’s worth noting that you shouldn’t apply any soundproofing materials directly to the boiler. Soundproofing materials are often very effective heat insulators, and so putting them on the boiler could lead to bigger problems.

However, if you’re intelligent about how you approach the problem then this shouldn’t be an issue. Here are my top solutions for how to soundproof a boiler:

1. Don’t overlook regular maintenance

The first thing you should always do is to ensure your boiler is properly maintained. This will hopefully reduce the chances of any of the above issues occurring, meaning you’re only presented with standard boiler noises.

Have your boiler inspected at least once a year by a trained engineer. A properly maintained boiler can work for over 20 years with minimal issues, which makes the price of an annual service very cost-effective.

2. Soundproof the boiler cupboard

A much more effective solution to soundproofing the boiler itself is soundproofing the cupboard it’s stored in. Even in a small boiler cupboard, you should be able to install enough soundproofing materials to make a difference.

Before starting, check your boiler manual for information on how much space your boiler needs. Most will need around 10 inches of space above and 4 inches of space below, but this can vary between brands.

The best products you can use to soundproof a boiler cupboard are:

Mass loaded vinyl

Mass loaded vinyl (Amazon) is one of the best soundproofing materials out there. It’s what’s known as limp mass, meaning it doesn’t vibrate when hit with sound waves. Instead, they simply dissipate rather than transferring their energy to the material.

Its main advantage in this situation is that it’s fairly thin, meaning there’s less chance of it impacting the boiler. However, MLV is quite heavy, so you might find the installation to be difficult.

The easiest way around this problem is to fix the MLV to a sheet of plywood or similar material, which can then be fixed to the inside of the boiler cupboard.

Acoustic insulation foam

Acoustic insulation foam (Amazon) is another great product to use here for many of the same reasons. It’s generally a sheet of dense fiber, which helps to deaden any noises.

Its advantage here is that it’s easier to work with than MLV, but is best used with another product to help deaden the sound even more. For example, it would work best fitted to a piece of acoustic drywall, which can then be fitted to the inside of the boiler cupboard.


Rockwool (Amazon) is basically fiberglass thermal insulation that’s designed for soundproofing purposes. It’s fairly dense but has a structure that’s open enough to trap sound waves, preventing them from resonating off a flat surface.

Although I’d like to hope it would never get to this point, Rockwool is also fire retardant. This means it’s possibly one of the best products to use in a boiler cupboard because it’ll at least protect you if there is a fire.

It almost goes without saying, but I’d generally try and avoid using soundproofing materials that could become a fire hazard, such as acoustic foam or soundproof curtains.

Although modern boilers are generally fairly low risk when it comes to fires, there seems little point in adding flammable materials into the mix, as this is only going to make things worse.

Also, it’s worth bearing in mind that you’ll need to monitor your boiler more regularly if you soundproof its cupboard. After all, there’ll be a much lower chance of you noticing any problematic noises if you can’t hear anything coming from the cupboard.

To overcome this problem, simply check it once a week while it’s working. If you combine this with a quick look at the pressure gauge then you should cover all your bases easily.

3. Soundproof the door and floor

After tackling the walls, the next best thing to do is to soundproof the door, and the floor if you want to go all out. Anyone familiar with soundproofing will know that doors are one of the weakest spots in a room for sound leakage.

How you confront this problem will depend on where your boiler is stored. If it’s in a broom closet with a normal internal door, then it’s worth switching this for a solid one because it’ll make a massive difference.

If the boiler is inside a kitchen cupboard or similar then you need to go about it differently. The best way to soundproof a cupboard door is to add some soundproofing materials to it, just the same as the walls.

The best thing to use is the thinnest but densest soundproofing material, such as MLV. This will take up the least space, which should hopefully have little impact on your boiler. Check out this website for some more specific kitchen soundproofing products.

For soundproofing the floor, you’d be best to use some acoustic insulation foam or similar. However, this is probably the last area you should tackle, and won’t really make a massive difference.

Unlike something like a washer or dryer, it’s unlikely your boiler sits directly on the floor and is instead attached to the wall. Therefore any sound created won’t pass into the floor directly.

4. Upgrade your system

Possibly one of the easiest ways to reduce the overall noise your boiler makes is to replace it with a newer model. However, this is probably only applicable if your boiler is over 10 years old.

Many modern combi boilers are almost silent other than the pump. So if you pay to have the system flushed, install a sludge filter and then fit a new boiler, you should notice a massive difference to overall noise levels.

Replacing a boiler isn’t the cheapest option but if you spread the cost over the boiler’s lifespan then it doesn’t work out too expensive. While this won’t completely soundproof a boiler, it’s an easy way to reduce the noise it makes in the first place.

Some final thoughts

If your boiler is making noise then the first thing you need to do is check it’s functioning properly. Providing this is the case, there are a few soundproofing methods you can try. However, I recommend that you do so with caution and always follow any recommendations in the boiler’s manual so as to prevent fire.

Also read: Is A Noisy Boiler Dangerous?