Boilers often make more noise when the heating is running, but a noticeable increase can indicate changes in pressure, flow, or internal components.
Kettling noises, humming, or whirring sounds are commonly linked to restricted water movement. When water can’t circulate freely, it heats unevenly and creates noise inside the boiler.
Air in the system can also cause sound changes, particularly when the pump is working harder to push water through partially blocked sections. Over time, this can affect both noise levels and heating performance.
Limescale buildup in heat exchangers is another factor, especially in hard water areas. This reduces efficiency and can make the boiler work harder, increasing noise during operation.
Boiler noise often ties back to overall system health rather than a single fault. The relationship between circulation, efficiency, and comfort is part of the broader picture covered in WarmGuide’s main overview.
If the boiler is louder than usual but still heating effectively, it’s often an early warning rather than an urgent failure.