Why is my boiler making banging, gurgling or whistling noises?
Most boiler noises map to a known cause: a rumbling 'kettling' usually means limescale or sludge on the heat exchanger; gurgling is usually trapped air or low pressure; banging on start-up can be delayed ignition — that one's worth an engineer promptly; tapping and ticking is often normal thermal expansion; whistling tends to be flow restriction or a pump issue. The pattern (when it happens, where it's loudest) tells most of the story — a short video with sound lets us tell you which you have before anyone books anything.
The one to take seriously
Banging or booming at start-up can indicate delayed ignition — gas building before it lights. Don't keep resetting a boiler that's doing this; have it looked at promptly. It's exactly what safety devices and engineers exist for.
The most common: kettling
Sludge and scale insulate the heat exchanger so water boils where it shouldn't — the rumble of a kettle. A proper flush usually sorts it and the system heats better afterwards. Ignored, it shortens the boiler's life.
The harmless ones
Gentle ticking as pipes warm and cool is thermal expansion — normal. Brief gurgles after bleeding radiators, likewise. If the noise is new, loud or getting worse, that's the cue to ask.