Most of these sounds are harmless and part of normal operation.
Common sounds
Action
Monitor the boiler and keep an eye on any changes.
Persistent noises may indicate a developing fault.
Common sounds
Action
Arrange an inspection if the noise continues.
Some noises may indicate a serious fault.
Warning signs
Action
Switch the boiler off and call a Gas Safe engineer.
We provide fast, reliable plumbing and heating services across South West and Central London, covering both residential and commercial properties.
Banging noises are often caused by trapped air, limescale build-up, poor water circulation or internal component faults. While occasional knocking isn't always serious, loud or repeated banging should be investigated by a Gas Safe engineer.
Whistling usually occurs when water is forced through a restricted opening or when pressure inside the system is too high. It can also be a sign of limescale build-up within the heat exchanger.
Boiler kettling describes a rumbling or boiling sound caused by limescale restricting water flow through the heat exchanger. As water overheats, steam bubbles form and collapse, creating the distinctive noise. Left untreated, kettling can reduce efficiency and damage boiler components.
Not always. Some boilers naturally make quiet operational sounds. However, loud banging, persistent whistling, burning smells or noises accompanied by leaks or fault codes should never be ignored. If you're concerned about the safety of your boiler, arrange a professional inspection.
Vibrating noises may be caused by a worn circulation pump, loose internal components or heating pipes moving as hot water flows through the system. A Gas Safe engineer can identify the exact cause and recommend the appropriate repair.
Yes. Low pressure can affect water circulation and may cause unusual noises, particularly if air has entered the system. If your pressure repeatedly drops below the recommended level, read our Boiler Losing Pressure guide or contact Keystone for further advice.
Yes. Keystone provides boiler diagnostics and repairs throughout London. Our experienced Gas Safe engineers work on all major boiler brands and can diagnose problems such as kettling, pump faults, circulation issues and unusual boiler noises.
The cost depends on the underlying fault. Some problems require simple adjustments or servicing, while others involve replacing components such as pumps or valves. Keystone provides transparent quotations after diagnosing the issue, so you'll know exactly what repair is required before any work begins.
Yes. Our engineers repair and service many of the UK's leading boiler manufacturers, including Worcester Bosch, Vaillant, Ideal, Baxi, Glow-worm, Viessmann, Alpha, Potterton and more. Whether your boiler is making unusual noises, displaying fault codes or has stopped working altogether, we can help identify the cause and restore your heating safely.