Boiler making a noise? Banging, gurgling and whistling
Updated 7 November 2026
Boilers make a little noise when they fire up, but a new or louder sound usually means something has changed. The kind of noise is a good clue to the cause.
If you can smell gas, or a carbon monoxide alarm goes off, stop and call 0800 111 999.
Banging or rumbling, like a kettle
This is often called kettling. Sludge or scale builds up on the boiler's heat exchanger, the water trapped there overheats and boils, and you hear it rumble or bang. It tends to get worse over time and makes the boiler work harder. An engineer can confirm it, and the usual fix is cleaning the system, often with a power flush, plus a magnetic filter to stop it coming back.
One loud bang when it lights
A single bang or boom as the boiler fires up can mean the gas is lighting late. Turn the boiler off and get an engineer out. It can damage the boiler and isn't safe to leave.
Gurgling
Gurgling from the radiators usually means air in the system. Bleeding them and topping the pressure back up often cures it, and our guide to cold radiators shows how. Gurgling from the boiler itself in freezing weather, along with a fault code, is the classic sign of a frozen condensate pipe.
Whistling or screeching
A whistle can be kettling at an early stage, or low water pressure, so check the gauge reads about 1 to 1.5 bar when the heating's off. A high-pitched screech or grinding from inside the boiler is more likely a fan or pump bearing wearing out, which needs an engineer.
Humming or vibrating
A steady hum often comes from the pump running too fast, or from pipes that aren't clipped down properly and vibrate against walls or floors. Neither is dangerous, and an engineer can turn the pump speed down or clip the pipes.
Clicking but not lighting
If the boiler clicks over and over but doesn't fire, it's trying to light and failing. Our guide to a boiler that won't fire up covers what to check.
What you can check yourself
- The pressure gauge. Top it up to about 1.2 bar if it's below 1. See why a boiler loses pressure.
- Air in the radiators. Bleed any that are cold at the top.
- The condensate pipe, if it's below freezing outside.
Never take the boiler's casing off. Only a Gas Safe registered engineer can legally work on a gas appliance.
When to call an engineer
Get an engineer if the noise comes with a fault code that won't clear, if the boiler bangs as it lights, or if a noise keeps getting louder. Tell them what it sounds like and when it happens, as that helps them bring the right parts.
Need it sorted? Boiler repair in Newcastle typically costs £150 to £450. A local engineer will give you a price before starting.