Boiler kettling & boiler making noise: 3 possible causes

Boiler kettling refers to many different types of unwanted boiler noises. It’s usually a result of overheating due to limescale. However, there can be other causes. If you have a noisy boiler, this article will help you understand why it’s making strange sounds and what can be done to fix it.

Boiler kettling explained

Most boilers aren’t silent – they usually make a little bit of sound as part of their normal operation. This may be from the whirr of the pump or the hum of a fan. However, in some cases, the sounds can be really conspicuous, like whistling, rumbling, banging, gurgling, fizzing, and so on. In many cases, the sound often resembles a kettle as it brings water to the boil, hence the term ‘kettling’.

Over time, limescale forms in the boiler’s heat exchanger, much as the same way as it does over the element in your kettle. As the water is heated, bubbles of air become trapped underneath the limescale. The sound is the result of these air bubbles expanding and bursting. Unsurprisingly, boilers in hard water areas are prone to this.

Before spending a couple of thousand pounds on a new boiler, a possible solution may be to add descaling chemicals to the system, letting them act slowly, and then draining or powerflushing them out at a later date.

Other reasons for boiler kettling

Flow rate

Poor water flow rate is another possible reason for boiler kettling. The slower the flow of water through the heat exchanger, the less energy is required to heat the water to a given temperature. The end result is that the water is hotter than it should be, which can result in bubbling or boiling sounds. (The word boiler is actually a bit of a misnomer, as the water is never brought to boiling point.)

Poor flow rates can be caused by poor installation or the build-up of limescale and sludge. These will restrict the flow of water through the heat exchanger. Once again, a power flush may resolve the issue. After this, inhibitor and descaling chemicals should be added to the system to prevent the problem from occurring again.

Blocked condensate pipe

A blocked or frozen condensate pipe may cause condensate to collect in the sump, making a bubbling or gurgling sound before eventually triggering a fault code and stopping the boiler from working. For more information on this fault, see the following page: Frozen condensate pipe: how to fix

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