Unraveling the Mystery: Why Is My Boiler Making Noise?

April 28, 2023 | News

Vaillant boiler making noises

Boilers play a vital role in maintaining a comfortable temperature within our homes. However, when they begin to make strange noises, it’s natural to become concerned. In this comprehensive guide, we will delve into the various noises a boiler might make, their causes, and how to address them.

Table of Contents

  1. Boiler Kettling
  2. Gurgling Noises
  3. Drone Noises
  4. Humming Noises
  5. Whooshing Noises
  6. Is a Noisy Boiler Dangerous?

Boiler Kettling

Boiler kettling is a phenomenon where water inside the boiler reaches boiling point, generating steam and trapping air. This causes a distinctive whistling or banging noise. Kettling can result from various factors, including:

  • Limescale buildup
  • Faulty thermostat
  • Damaged pump

Limescale Buildup

Homes in hard water areas are prone to limescale buildup within pipes, which can restrict water flow. Slowed water flow causes water to overheat, leading to boiler kettling.

Faulty Thermostat

A malfunctioning thermostat might provide incorrect readings to the boiler, causing it to heat water to dangerous levels. This is more common in older boilers nearing the end of their lifespan.

Damaged Pump

The boiler pump is responsible for circulating water throughout the system. If it’s damaged, water flow can be reduced, resulting in overheating and kettling.

Solution: Call a Gas Safe registered engineer to inspect your system. Depending on the cause, they may perform a chemical clean, power-flush, or replace faulty components.

Gurgling Noises

Gurgling noises are often caused by trapped air in the system, which mixes with the water. While not a severe problem, it should be addressed promptly. To resolve this issue:

  1. Turn on your heating system and wait for the radiators to warm up.
  2. Feel the surface of each radiator to identify cooler areas, which may indicate trapped air.
  3. Turn off the heating and allow the radiators to cool.
  4. Use a radiator key to bleed each affected radiator.
  5. Check the water pressure on your boiler and verify if the gurgling noises have stopped.

Drone Noises

Drone noises, reminiscent of an airplane taking off, can be attributed to various factors. A common cause is a faulty pump.

Solution: Contact a specialist to diagnose and address the issue. Replacing the broken pump is usually the most effective course of action.

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Call our specialists on 020 8395 8616 or fill in our booking form.

Humming Noises

Humming noises can occur when water from the mains enters at excessive pressure, causing valves in the boiler or pipes to hum. It can also result from a pump circulating heated water too quickly or worn bearings in the boiler fan.

Solution: Consult a boiler engineer to inspect the issue. If it’s related to the boiler pump or fan, they will need to remove the boiler casing and make the necessary repairs.

Whooshing Noises

Whooshing noises often originate from:

  • Air intake pipe blockages
  • Air filter blockages

Solution: Call a Gas Safe engineer to diagnose and address the issue. While some blockages may be apparent, others require the expertise of a professional.

Is a Noisy Boiler Dangerous?

While a noisy boiler can be concerning, it’s typically not an immediate danger. Boilers are equipped with safety mechanisms to shut down before becoming hazardous. Nevertheless, it’s crucial to have a boiler engineer inspect your boiler as soon as possible to identify and resolve any issues.


Boilers can make various noises, each indicating a specific issue:

  • Boiler kettling: Water reaches boiling point inside the boiler, generating steam and trapping air. This can result from limescale buildup, a faulty thermostat, or a damaged pump.
  • Gurgling noises: Caused by trapped air, which can be resolved by bleeding the radiators.
  • Drone noises: Often due to a faulty pump, requiring replacement by a qualified heating expert.
  • Humming noises: May be caused by excessive water pressure, a pump circulating water too quickly, or worn bearings in the boiler fan.
  • Whooshing noises: Result from blockages in the air intake pipe or air filter.

Although a noisy boiler is not typically dangerous, it’s essential to have a boiler engineer investigate and resolve the issue as soon as possible.

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