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Last updated: 23rd April, 2024


Why is My Boiler Making a Humming Noise?

Why is My Boiler Making a Humming Noise?

Key takeaways

  • A humming boiler often signals a malfunction or a necessary repair.
  • Correctly diagnosing the cause of the noise can prevent further damage.
  • Maintenance and timely professional assessment are essential to boiler health.

Boiler noises are frequent issues that signal varied problems within the system. From slight humming to pronounced banging, each sound could indicate a specific malfunction or condition needing attention.

A humming noise in your boiler can indicate a variety of issues ranging from minor to serious. It is a common problem encountered by many homeowners, where the boiler emits persistent hums that can be either soft or loud enough to cause concern. This sound often points to an underlying functional issue, which could affect the boiler's efficiency or even pose a potential safety risk.

Boilers are complex appliances, and their internal workings involve a number of components that must interact seamlessly to provide consistent heat and hot water. When a component does not function as it should, noises like humming can occur. 

The causes of this humming can be as simple as a loose part, or as serious as a problem with the central heating pump or an issue with electric elements in electric boilers. It is essential for such symptoms to be diagnosed promptly to prevent further damage and to ensure the longevity of the appliance.

Whether it's due to a build-up of limescale, an issue with the pressure levels, or a faulty heating element, addressing the cause of a humming noise ensures your boiler operates smoothly. Regular maintenance and servicing can help to prevent such issues, but in some cases, professional intervention may be required to correct the problem and restore the boiler to quiet operation.

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Understanding Boiler Noises

Boiler noises are frequent issues that signal varied problems within the system. From slight humming to pronounced banging, each sound could indicate a specific malfunction or condition needing attention.

Common Types of Boiler Noises

  • Banging: Caused by a phenomenon called kettling, banging noises arise when water that is too hot converts into steam and expands, typically due to limescale accumulation in the heat exchanger.

  • Gurgling: This noise often reflects air trapped within the system or lower water levels, causing an uneven flow through the pipes.

  • Humming: A loud humming noise might suggest a pump running at an inappropriate speed or a failing component causing vibrations.

  • Whistling: Similar to a kettle boiling, this 'whistling' or 'whooshing' noise could stem from kettling caused by limescale or iron oxide sludge deposits.

  • Vibrating and Droning: Usually associated with an incorrect pump setting, these noises might occur when water rushes through the system.

  • Tapping and Clicking: Tapping sounds can be the result of a difference in water pressure or temperature within the boiler, while clicking might be an electrical issue.

  • Loud Humming Noises: Often linked to electrical issues or a pump working at the wrong speed, they require immediate attention to prevent further issues.

Noisy boilers are not inherently dangerous, but the sounds they produce can act as warning indicators of underlying issues. Prompt diagnosis and repair are essential to maintain the boiler's functionality and safety.

What is a Boiler Humming Noise?

A boiler humming noise is a consistent low-frequency sound that may indicate several potential issues within the heating system. It typically suggests something is amiss with the boiler's normal operation.

Why is my boiler making a humming noise?

There are various reasons a boiler might make a humming noise. One common cause is vibrations caused by imbalances within the system. Often, these are due to operational mechanisms like the central heating pump working harder than usual, or they may stem from loose components that resonate during use.

Another factor contributing to a humming boiler can be air caught in the system. When air is trapped, it disrupts the smooth circulation of water, resulting in vibrations and thus a humming noise. Resolving this usually involves bleeding radiators to release the air or even having the system professionally flushed.

Electrical issues can also manifest as a humming sound. For instance, if there's a problem with the thermostat or other electrical controls, they can generate noise as they struggle to function properly.

Moreover, limescale build-up can lead to a humming boiler. Especially in areas with hard water, limescale can accumulate on the boiler's heat exchanger, causing it to hum as it becomes less efficient and has to exert more effort to heat the water.

A humming noise might not signal immediate danger, but it shouldn’t be ignored either. It can be indicative of the heating system straining under preventable conditions, which could eventually lead to more severe problems if left untreated. Addressing these issues promptly, preferably by a professional heating engineer, is advisable to maintain the longevity and functionality of the boiler.

Possible Causes of Boiler Humming

When a boiler begins to hum, it often indicates a mechanical issue or imbalance within the system. This section explores some specific causes.

Faulty or Worn Components

A common source of humming is worn pump bearings in the boiler's pump. Over time, these bearings can deteriorate, leading to an incessant humming as the pump operates. In some cases, the pump itself may be faulty or malfunctioning, contributing to the noise.

  • Vibration: Loose components, such as internal screws or valves, may also vibrate under normal operation, causing a hum.

  • Pump: Could be set to a speed that is too high for the system's requirements, which in turn generates noise.

System Pressure Issues

Excessive pressure within the boiler can manifest as a hum. Conversely, low water pressure can strain the system as it attempts to circulate water, also resulting in a hum.

  • Overheating: When the system overheats due to pressure issues, the expansion of pipes might cause audible humming sounds.

Air in the System

Trapped air in the radiators or heating pipes can lead to a phenomenon known as boiler kettling, which produces a distinctive humming or rumbling noise.

  • Airlock: An airlock can disrupt the flow of water, hence the efficiency of the pump, leading to unusual sounds.

  • Bleeding your radiator: This is a method to remove trapped air and can often resolve the humming noise issue.

Boiler Maintenance and Solutions

Proper boiler care ensures efficiency and longevity. This section will explore preventative measures and solutions for common boiler concerns, particularly focusing on noise-related issues.

Preventing Limescale and Sludge

Limescale and sludge can significantly impair a boiler's performance. To combat this, a central heating inhibitor should be added to the system to minimise scale accumulation. Additionally, installing a magnetic filter can capture any sludge before it affects the heat exchanger. For critical cases, a powerflush of the system is recommended to clear out these impurities, which is best conducted by a Gas Safe registered engineer.

Boiler Servicing and Repairs

Annual servicing of your boiler is essential to maintain its functionality and safety. During a service, an engineer may identify parts in need of repair, such as a faulty thermostat or a frozen condensate pipe. They will also check safety mechanisms and inspect for leaks. If components like the boiler filter or heat exchanger are out of warranty and malfunctioning, timely repairs will save both energy and cost.

Troubleshooting Common Issues

When a boiler makes a humming noise, it is typically due to an issue within the heating system, such as a faulty thermostat or air in the system. To remedy this, one can try bleeding the radiators. However, more complex problems like heat exchanger malfunctions may require professional evaluation. For out-of-warranty boilers, seeking advice from a Gas Safe registered engineer is paramount.

When to Contact a Gas Safe engineer

When a boiler emits a humming noise, it can indicate various issues. Addressing these promptly by a qualified professional is crucial. It's important to understand when to engage a Gas Safe registered engineer.

How much does fixing a boiler humming noise cost?

The cost to fix a boiler humming noise depends on the complexity and source of the issue. It can range from a simple fix costing around £50 to more complex repairs upwards of £500. For instance, replacing a central heating pump can cost between £100 and £250. If a boiler's humming is due to ignition failure or a significant problem with the central heating pipe, expenses may be on the higher end. Here is a rough cost breakdown:

  • Simple Adjustments: £50 - £100

  • Pump Replacement: £100 - £250

  • Extensive Repairs: £250 - £500+

Please note that these costs can vary depending on the region and the specific Gas Safe engineer's rates.

Can I fix a boiler humming noise myself in any case?

Minor Adjustments:

  • Pressure Check: Ensuring the boiler pressure is within recommended levels.

  • Bleeding Radiators: Removing air that may cause noise in the system.

When not to DIY:

  • Gas Work: It's illegal to work on gas appliances unless Gas Safe registered.

  • Complex Components: Working on internal parts without proper training risks further damage and can be dangerous.

  • Warranty Concerns: DIY repairs could void your boiler's warranty.

For safety, legal, and warranty reasons, a certified Gas Safe registered engineer should address most cases of a boiler humming noise. They have the expertise to diagnose and resolve boiler problems efficiently and safely.

Importance of Boiler Servicing

Regular boiler servicing is fundamental to ensuring a heating system’s longevity, safety, and efficiency. A boiler’s performance can deteriorate over time, leading to a myriad of issues, with a humming noise being just one indicator of a potential problem.

Routine checks play a crucial role in preventing faults. They encompass inspection of the core components such as the heat exchanger, ignition system, and pump. These checks can reveal build-up of limescale or airlocks that could be causing operational issues. By addressing these during servicing, one reduces the risk of unexpected boiler breakdowns, which can be costly and inconvenient.

Professional servicing should include the assessment of the boiler's water flow rate and operating pressure. A certified technician will also check for leaks and test the system’s controls. This ensures that not only is the boiler functioning properly but also operating within safe parameters.

Boiler efficiency is another significant aspect impacted by servicing. A well-maintained boiler consumes less energy, indirectly leading to decreased energy bills and mitigating unnecessary environmental impact. Servicing ensures that boilers are not overworking due to unresolved internal problems, therefore maintaining energy efficiency.

Moreover, regular servicing ensures compliance with warranty requirements. Manufacturers often necessitate yearly servicing as a condition for maintaining the validity of the boiler’s warranty. Without these services, owners might find themselves facing the full costs of repair or replacement, should issues arise.

In conclusion, annual servicing of a boiler is indispensable. It assures peace of mind for homeowners by keeping energy costs low, warranting safety, and preempting the disruptions caused by breakdowns.


Do I Need A New Boiler?

When a boiler begins to emit a humming noise, it raises concerns about whether a replacement is necessary. In many cases, the humming is indicative of fixable issues rather than a sign that the boiler needs to be replaced entirely. The following are common rectifiable causes:

  • Air in the System: Trapped air can lead to vibrations that manifest as humming. Bleeding the radiators is a straightforward remedy.

  • High Pressure: Excessive pressure within the central heating can also result in a humming noise. Adjusting the pressure to the correct level may require professional assistance.

On the other hand, persistent noises, despite troubleshooting, might indicate more serious internal problems such as:

  • Failed Components: Worn-out bearings or a faulty central heating pump.

  • Scale Build-up: Often referred to as 'kettling', which could necessitate descaling or part replacement.

Before contemplating a new boiler, evaluate the age and performance of the current system. Boilers have a typical lifespan of 10-15 years. If the boiler is approaching or has surpassed this age and is frequently breaking down or requires expensive repairs, replacement may be the more cost-effective option in the long term.

It is essential to consult with a certified heating engineer, who can provide a precise diagnosis and advice. If the issue is complex and the boiler is relatively old, they may suggest considering a new, more energy-efficient model. However, if the boiler is younger or the humming is due to a minor issue, repairs could well extend the life of your boiler significantly.

iHeat New Boiler Costs

Boilers can be a daunting purchase for many people as they’re an appliance with a lot of responsibility, providing heat for you and your family is something you want to get right. Boilers aren’t exactly a quickly disposable item either, potentially lasting you a decade.

Effectively, new boiler cost can be split into two segments: the first is the actual boiler itself (unit price), and the second is the cost of the boiler being installed (set up) in your property by an expert engineer. 

Here at iHeat, we want to remove all of this undue stress and make the decision making process of upgrading to a new central heating system, as easy as possible.

Boiler costs can vary depending on a number of factors including their brand, model, fuel, output, warranty, labour and installation type. Typically a new boiler will cost between £1,845 and £3,500, below is a list of average boiler installations offered by iHeat (guide only).

Installation Type

Price (inc VAT)

Combi to combi swap


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System to combi conversion


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New boiler install


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Back boiler to a combi


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System to system


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Frequently Asked Questions

How do I stop my boiler from humming?

To stop a boiler from humming, one should check the pressure gauge. If it's above 1.5 bar, the pressure is too high and may need adjustment. Ensuring that the speed setting on the pump is correct can also eliminate humming sounds.

When should I worry about boiler noises?

Worry is warranted if boiler noises are loud, persistent, and accompanied by other signs of malfunction, like leaks or failure to heat. A qualified heating engineer should be consulted to assess the noises and the boiler's condition.

Why is my boiler making a weird noise?

Weird noises from a boiler often point to trapped air, high water pressure, or limescale accumulation. Identifying and rectifying these core issues can help in reducing or eliminating the noise.

Why is my boiler pump making a humming sound?

A boiler pump may hum if it's operating at a speed not suited to the system's requirements, or if there is a defect within the pump. It's essential to check the pump settings and, if necessary, seek professional help to investigate further.

What does a bad boiler pump sound like?

A failing boiler pump can manifest as a range of noises from humming and buzzing to grinding or gurgling. Any unusual sound should prompt a thorough check or a professional's diagnosis.

What does a boiler pump sound like?

Normally, a boiler pump will emit a low, steady humming sound indicating it's functioning correctly. Any significant deviation from this baseline noise level might suggest an issue that needs attention.

Stephen Day profile photo
Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.