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Unusual Boiler Sounds Explained

When your boiler starts to make an unusual noise it can be cause for concern. It might be the sign of something awry which needs addressing as soon as possible. Quite often addressing the issue early works out far cheaper (and is far safer). On this page you'll see a variety of boiler noises explained, and some possible fixes. As always when it comes to repairing your boiler, please don't undertake any work yourself unless you a re fully qualified to do so.

Can you hear a vibrating noise from your boiler?

Vibrating noises coming from a boiler can be caused by several different issues. Common causes of vibrating noises include:

  • Expansion and Contraction: Over time boilers will expand and contract due to changes in temperature or pressure inside the unit. This expansion and contraction can create vibrations that cause an audible noise.
  • Imbalanced Radiators: If radiators are not balanced correctly on the wall brackets they may become loose over time which could cause them to vibrate against the walls as hot water passes through them.
  • Air in System: If there is air trapped in your heating system it can cause loud rattling and banging sounds as it moves around when heated up by your boiler’s burner flame or fan motor.
  • Faulty Pump: A pump with electrical faults or worn bearings may produce an unpleasant humming sound that intensifies with use as its components start to wear out over time.
  • Kettling Noise: Kettling is a common issue where limescale deposits build up inside your boiler causing ‘knocking’ type noises when hot water passes through these areas of blockage.
  • Leaking Seals: Degraded seals between components such as pipes and valves could also allow steam or water to escape producing hissing or whistling noises that indicate a leak somewhere in the system.
  • Loose Parts: Many modern boilers have plastic parts surrounding certain internal components like fans and motors which if become loose will rattle noisily whenever they move due to vibration created by their operation.
  • Incorrectly Fitted Components: Poorly fitted radiators, flues, pumps and other accessories are all potential sources of noisy vibrations and should always be installed correctly according to manufacturer guidelines for best results.

How do you stop boiler vibration noises?

There are various methods you can use to reduce or stop vibrating sounds coming from your boiler including:

  1. Balancing Your Radiators – To reduce any potential noise from imbalanced radiators ensure they're securely fixed on their wall bracket before refilling your central heating system with fresh inhibitor fluid prior turning it back on again post-installation.
  2. Bleed The System - Remove any air pockets present within your radiator circuit (including individual radiators) using either traditional manual bleeding techniques (using keys/radiator bleed screws), powerflushing equipment or simply install automatic lockshield valves at each end of every run pipe throughout home for automated continuous circulation.
  3. Replace Any Worn Parts - Inspect all moving parts such as pumps, fans and motors for signs of wear before replacing if necessary with genuine spares recommended specifically by manufacturers.
  4. Insulate All Pipes - Make sure all pipes connected directly onto external walls have adequate insulation applied around them regularly during cold weather months so prevent condensation forming leading possible freezing then bursting thus creating unwanted noise levels while running etc.

Buzzing or droning type noises

A droning noise is a low pitched humming or buzzing sound which may come from your boiler usually when it’s in operation. This type of noise is often caused by an imbalance in the pressure between components within the system or a fault involving bearings inside the motorised pump or fan unit. It may also occur due to loose bolts or fasteners on certain parts of the appliance such as flue pipes or air intakes causing vibration throughout its structure and generating noise as result of this movement.

Causes Of Boiler Droning:

  • Faulty Bearings: Worn bearings within pumps/fan units can cause vibrations resulting in irritating low-pitched drone sounds.
  • Pressure Imbalances: An imbalance between different components such as water pressure vs gas pressure could lead to fluctuating pitches during operation.
  • Loose Parts/Fasteners: If any part of your system isn’t securely fitted it may generate unwanted rattles and buzzing.

How Do You Stop Them?

If you're experiencing annoying buzzing noises coming from your boiler then there are some steps you can take to try and fix them yourself before calling out an engineer for help:

Check All Fastenings Are Securely Tightened – make sure all nuts and bolts on external panels (flue pipe) as well other moving internal parts (pumps) are properly tightened so they won't vibrate against each other.

Check For Blockages Or Leaks - check for blockages anywhere along pipework leading up into/out from appliances; leaks could also account for unusual amounts of air being drawn into combustion chamber creating turbulence and producing loud whistling sounds. Make sure everything is sealed correctly using tape/sealant if necessary.

Is your boiler making a humming noise?

Humming noises coming from a boiler can be caused by several different things. It could be due to the circulation pump which is responsible for pumping water around the central heating system and radiators. Alternatively it could be because of an issue with the diverter valve meaning that water is not being diverted between hot and cold correctly. The most likely cause of humming noises coming from a boiler is usually sediment buildup in the bottom of the tank or heat exchanger causing cavitation. This occurs when a gas bubble forms in water and then collapses rapidly creating vibrations which create noise as they pass through pipes within your system.

How do you stop boiler hum?

If you believe that humming noises coming from your boiler are due to sediment build up in your tank or heat exchanger there are some steps you can take to try to reduce them: Firstly make sure all air vents on radiators and pipework leading into your boiler have been opened so any trapped air can escape; Secondly ensure that all filters throughout your system have been checked regularly and cleaned if necessary; Lastly check if there's an increase in pressure on either side of any valves such as those located near pumps – this should help identify if there’s anything blocking its passage through pipes (such as debris). If these steps don't resolve the issue then it might require professional attention so contact a qualified engineer who will assess whether further repairs/maintenance needs doing before recommending remedial action.

Gurgling noise coming from your boiler

Gurgling noises coming from your boiler can be a cause for concern and should be checked by a qualified engineer. This type of noise is usually caused by air or water trapped within the system which can lead to damage and reduced efficiency if not properly addressed.

Common Causes of Gurgling In Boilers:

  • Blockages in pipes or radiators due to sludge build up
  • Air bubbles in the system that are unable to escape
  • Low water pressure due to incorrect installation or wear and tear over time

Symptoms of Gurgling Noises:

  • Loud gurgles when heating turns on/off
  • Boiler making bubbling sounds when running
  • Radiators not heating up as quickly as usual

How to stop your boiler making gurgling noises

  • Bleed Radiators: If you hear loud gurgles coming from your radiators then this could indicate that they need bleeding. Air may have become trapped inside them so it’s important to release it before the problem worsens otherwise further damage may occur. Make sure you use an appropriate radiator key for this task and take care not over tighten it!
  • Check Water Pressure: Low water pressure can also cause gurgles so check the gauge on your boiler display panel, ideally it should read between 1 and 2 bars (if your model has one). If necessary adjust accordingly using instructions provided with your manual or contact an experienced technician who will be able to help reset correctly.
  • Flush The System: Sludge build up is another common cause of gurgle noises so flushing out any blockages with chemicals might do the trick here too.

Loud banging noises

If your boiler is making banging or thumping noises it can be quite alarming. There are a few potential causes of this and understanding the source of the noise is important in order to resolve it.

Common Causes

The most common causes for banging noises from boilers are:

  • Kettling: This occurs when limescale builds up inside the heat exchanger restricting water flow and leading to boiling within the system. The resulting steam pressure then forces its way through any weak points in the system creating a loud bang or clunking sound.
  • Expansion tank issue: If water pressure rises too high due to a faulty expansion vessel it may cause pipes to vibrate which can produce an audible banging sound as they expand due to increased temperature.
  • Blocked air vents/pump failure: When air vents become blocked by dirt and debris, pressure within your boiler will build causing pipes and components within it to vibrate which could lead you hearing banging noises if not resolved quickly enough. Similarly pump failures could also lead to similar issues with vibrations being created as hot water flows around your central heating system.

How do you stop your boiler from making a banging noise?

In order for you stop these kinds of noises coming from your boiler there are several steps that you should consider taking;

  1. Check Your Pressure Levels: Firstly check that your expansion vessel has sufficient pressure levels by looking at either on top of its casing or at its dials (if fitted). It should usually read between 1-2 bar but consult with manufacturer guidelines before making any changes yourself.
  2. Have It Serviced Regularly: To prevent kettling occurring make sure that you have regular servicing done on your boiler so any limescale buildup can be removed professionally before becoming an issue .
  3. Clean Out Air Vents: Make sure all air vents connected into radiators throughout your home are free from dust & dirt as these may block airflow over time which increases pressures internally leading them becoming noisy.
  4. Replace Faulty Pumps: Lastly if none of these other solutions work then its possible that one of pumps attached onto radiator might need replacing due too age or wear and tear caused by rust etc. Seek professional advice first though!

Kettling Noise

Kettling is a loud rumbling noise that can be heard when your boiler is working. It’s caused by limescale deposits building up inside the heat exchanger of your boiler and it can be very alarming.

Causes of kettling:

  • Limescale buildup inside the heat exchanger
  • Blockages in water pipes due to sludge or debris
  • Low pressure in the system which causes steam bubbles to form and burst

How to diagnose kettling noises:

There are several ways you can diagnose kettling noises coming from your boiler. These include listening for vibrations, checking for blockages and testing water pressure levels. Here are some steps you can take to help identify what's causing the noise:

  • Listen carefully while the heating system is running – try turning off other appliances near the boiler so you can isolate any abnormal sounds; this will help pinpoint where they're coming from.
  • Check all visible pipework for signs of blockage or damage; if there are any obstructions then these could be contributing to kettling noises as well as reducing efficiency in your system.
  • Check water pressure levels; if they're lower than normal (below 1 bar) then this could also cause kettling sounds as steam bubbles form and burst within pipes/radiators due to low flow rates across them during operation.

How do you stop kettling noises?

  1. Descale Your Boiler – Have an engineer descale your central heating system which will remove any build-up of limescale within it and should reduce/eliminate any further build-ups going forward too. This should get rid of most common sources noise quickly!
  2. Flush Out andReplace System Water – An engineer may suggest flushing out old warm air pockets before replacing with fresh cold mains water; doing so helps improve circulation throughout radiators/pipes etc., thus reducing chances for steam bubbles forming again over time (which would produce similar types' rattles).
  3. Replace Heat Exchanger Parts – If descaling or flushing don't work then parts like seals/gaskets around heat exchangers may need replacing too since these often degrade through use.


If you hear any unusual sounds coming from your boiler system it is essential that you do not ignore them. If left undiagnosed these problems can lead to significant damage and even complete failure of your boiler system. We strongly recommend seeking assistance as soon as possible from our network here at UK Boiler Quotes who have extensive experience in diagnosing and resolving all kinds of heating related issues quickly and safely.

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