Why Is My Boiler Noisy? Common Causes & How to Fix It

If your boiler has started making banging, whistling or gurgling noises, it’s trying to tell you something. Strange boiler sounds can range from harmless to urgent — here’s how to tell the difference and what to do about it.

1. Kettling

Sound: Loud banging or rumbling

Cause: Limescale or sludge build-up restricting water flow in the heat exchanger, causing water to overheat and steam.

Fix: A system flush (chemical or power flush) by a professional to remove debris and restore water flow.

2. Air in the System

Sound: Gurgling, bubbling or occasional banging

Cause: Trapped air in radiators or pipework.

Fix: Bleed your radiators to release trapped air. If the problem persists, the system may need balancing.

3. Low or High Water Pressure

Sound: Whistling or knocking noises

Cause: Incorrect pressure (should usually be between 1.0–1.5 bar).

Fix: Check the pressure gauge and top up or bleed the system as needed. If pressure drops repeatedly, call an engineer.

4. Faulty Pump or Fan

Sound: Grinding, humming or vibrating

Cause: Worn or malfunctioning internal components.

Fix: This needs a Gas Safe registered engineer. Continued use could damage the boiler.

5. Expansion and Contraction

Sound: Tapping or clicking, especially when heating turns on or off

Cause: Normal expansion of pipes or metal as they heat up and cool down.

Fix: Harmless in most cases. Ensure pipe clips are secure to reduce movement noise.

6. Limescale Build-Up (Hard Water Areas)

Sound: Hissing, bubbling or kettling

Cause: Limescale accumulating on heat exchanger surfaces, common in hard water areas like Fife.

Fix: Fit a scale reducer and have a limescale flush carried out if needed.

7. Blocked or Partially Closed Valves

Sound: Whistling or screeching

Cause: Obstructed flow through valves or partially closed radiator valves.

Fix: Check and fully open radiator valves. If unsure, get a professional to inspect your system.

Should I Worry About Noisy Boilers?

Some noise is normal, especially during ignition or cooling. But if your boiler’s sound has changed suddenly or grown louder, it’s worth investigating. Left untreated, minor issues can escalate into breakdowns or costly repairs.

When to Call a Heating Engineer

• Persistent banging, hissing or loud noises
• Pressure keeps dropping
• No heat or hot water
• Burner fails to ignite

It’s always best to call in a Gas Safe registered engineer to avoid guesswork and ensure a safe, lasting fix.

Need Help With a Noisy Boiler?

We diagnose and fix noisy boilers across Dunfermline, Kirkcaldy and Fife. Whether it’s trapped air, a faulty pump or a failing heat exchanger — we’ll sort it.

📞 Call us: 01383 660098
🌐 Visit: jones-heating.co.uk/boiler-repairs

We’ll get your heating back to silent, safe, and efficient — no more mystery noises.