Boiler expert explains the sounds you should never ignore and when to call an engineer

A boiler on the blink can be the difference between a good day and a bad one. There's nothing quite like waking up in the morning and finding that either the heating has not come on or your shower is freezing cold.

And while both of those things are unpleasant the potential for a costly repair, or even replacement, is even more horrible. Avoiding either then, is crucially important and keeping an eye on the sounds your boiler makes is something everyone can do.

Andy Kerr, founder and CEO at BOXT, has issued advice for homeowners, saying: "If you've noticed your boiler making a noise that varies from how it usually sounds, it's best to act fast to prevent further damage. A noisy boiler isn't always a cause for concern, but there are certain noises to look out for, and each comes with its reasons and remedies."


Kerr explains that one common issue causing a noisy boiler is kettling, which occurs when water flow through the boiler slows, leading to overheating and boiling point, hence the kettling noise. Often this is due to circulatory problems, indicating that water isn't being effectively pumped or moved around the system. This could be a sign of a faulty pump or central heating system issues.

He warns that kettling can be a significant issue and should be inspected by a Gas Safe engineer. Common causes include limescale build-up, a leaking boiler or incorrect water levels, a malfunctioning thermostat causing the boiler to overheat, or a faulty pump.


Kerr also notes that a clicking or tapping noise might mean the boiler is having trouble igniting, potentially due to ignition failure. He stresses that this is not a DIY fix and recommends contacting a Gas Safe engineer, as it may relate to the property's gas supply.

Dripping sounds

These noises are often caused by trapped air in your radiator. Sometimes, the gurgling sound coming from your boiler is just the hot water moving, so there's no reason to worry.

However, if the sound is persistent and happens more frequently, it's best to take a quick look at the following....

  • Bleed the radiator: the gurgling sound could be stemming from an appliance associated with the boiler, such as a radiator. Once you have bled the radiator, check the boiler pressure and top it up if required. A drop in boiler pressure can lead to further issues. If the noises continue, the issue resides elsewhere.

  • Check the water pressure: low water pressure could be causing the gurgling noise. Take a look at the pressure gauge in your boiler cupboard, if the dial is in the red section the pressure is too low, and your boiler needs repressurising.

  • Check for a frozen condensate pipe: this often occurs during really cold weather, when outdoor pipes can freeze. Gently defrost the pipe with warm water to resolve this.

  • If the problem persists, there could be something else wrong with the boiler. Speak to a Gas Safe registered engineer who will be able to help tackle the situation.

Banging sounds

A loud banging noise from your boiler could be due to limescale buildup inside the heat exchanger, a malfunctioning boiler thermostat, or something as simple as an incorrectly set thermostat. It's advisable to call in a heating engineer who can examine the temperatures of your flow and return pipes for overheating, and also verify if your boiler thermostat is set at the correct temperature.

If these aren't causing the issue, they may need to inspect the pipework under your flooring to ensure it's properly clipped and supported. A Gas Safe registered engineer can also identify if the problem originates from your system circulation heat exchanger. In this case, a central heating system flush might be necessary to resolve the issue if it's due to a buildup of magnetite, debris or dirt.

Buzzing sounds

Hearing a buzzing sound from your boiler can be concerning, and it's best to consult a professional. A variety of issues could cause a buzzing sound, ranging from failing electrical components to a sticking pump.

If your boiler is making a buzzing or moaning sound, it's important to pay attention. Essentially, the whining noise is your boiler's way of asking for help. It indicates that immediate repair is needed, and you should call a professional to handle it.


Combi boilers are particularly prone to whooshing noises. These sounds, typically caused by a blocked circulation pump or trapped air in the system, should prompt you to contact an engineer. They can inspect for any blockages or trapped air and diagnose the issue.

Alarm sound

If your boiler is emitting an alarm sound, it's usually an indication that something isn't quite right. Common culprits include low water pressure, a faulty thermostat, and blockages. You can troubleshoot your boiler by checking the water pressure and the thermostat. If these are functioning correctly and the beeping continues, it's time to call a Gas Safe registered engineer.

Andy adds: "Remember, never attempt to fix anything yourself if you are unsure. Always call a professional if you're in any doubt about the noises coming from your boiler. Typically, the problems causing your boiler to make noise can be fixed quickly. But if your boiler is old and ready to be replaced, there's a chance that the problem might be something a little more severe and, in these instances, it's important to be aware that it might be time for a new boiler."