How to Diagnose Common Boiler Sounds

Knocking

"If you're hearing a clicking or tapping noise, it could be that your boiler is struggling to fire up," shares Kerr. "One potential cause for this is ignition failure. In this scenario, it’s not something you should try and resolve yourself, and instead need to call a professional as it could be related to the gas supply to your property."

Banging

Banging's louder than knocking. "A loud banging noise can come from buildup of limescale inside your heat exchanger, a faulty boiler thermostat, or it could be something as simple as your thermostat being set incorrectly," notes Kerr. "You might want to call a professional technician who can check the temperatures of your flow and return pipes to check for overheating, and also check your boiler thermostat is set to its correct temperature. If either of the above are not causing the issue, they may need to access the pipework under your flooring to check it is clipped and supported correctly."

A technician can also determine if the problem is coming from your system circulation heat exchanger. If it is, you may need a central heating system flush to fix the problem if it is a result of a buildup of magnetite, debris, or dirt.

Gurgling, Dripping, or Bubbling

Does your boiler make a sound like running water? "While there are other causes, for the most part, a gurgling noise is caused by trapped air in your radiator," highlights Kerr. "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 inspect the system." Consider doing the following:

• Bleed the radiator: "The gurgling sound could be stemming from an appliance associated with the boiler, such as a radiator," he notes. The bleed valve is easy to locate and radiator keys are inexpensive, making this a great DIY chore. "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 to balance the excess pressure."
• Check for a frozen condensate pipe: Frozen pipes occur during really cold weather. To warm and thaw a frozen pipe, wrap it in a warm towel, or use a lamp or blow dryer to slowly thaw the area that is frozen. A slow melt is best to prevent the pipe from bursting.

"If the problem persists, there could be something else wrong with the boiler," warns Kerr. Hire a boiler repair professional to help run further diagnostics.

Buzzing or Loud Humming Noises

Strange noises that involve buzzing warrant a call to a professional. "Numerous issues could cause a buzzing sound, from electrical components failing, to a boiler pump sticking," shares Kerr. "If you can hear your boiler making a buzzing sound, or it sounds like it's moaning at you, you should listen to it. Essentially, the whining noise is your boiler asking for help. It means it needs to get fixed immediately."

Whooshing

Whooshing noises are often described as the sound of a washing machine, and they're especially prevalent in combi boilers. "These loud noises coming from your boiler are usually made from a blocked circulator pump or trapped air in your system," diagnoses Kerr. "For this sound, you should schedule boiler repairs with a specialist who can check for any blockages or trapped air and diagnose the problem."

Alarm

"If there is an alarm sound coming from your boiler it’s usually a signal that something is not quite right," notes Kerr. "Common causes of this are low water pressure, a faulty thermostat and blockages. Troubleshoot your boiler by checking the water pressure and the thermostat settings. If these are in working order and the beeping sounds persist, contact a registered gas safe engineer."