Your radiators are making odd noises you haven't heard before – banging, gurgling, or hissing sounds. Here are some quick checks you can do yourself:
DIY Checks You Can Do
Check for air in radiators – Feel the top of your radiators. If they're cold at the top but warm at the bottom, they need bleeding. Use a radiator key to release trapped air until water comes out.
Check system pressure – Look at the pressure gauge on your boiler. It should read 1–1.5 bar. If it's low, you may need to repressurise.
Listen to where the noise comes from – Is it from one radiator or all of them? This helps diagnose the problem.
Can't Fix It Yourself?
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We're Advanced Heating and Plumbing, covering North London, West London, Watford, Herts and Middx.
Our vans carry many common spare parts so we can usually get things working in the same visit.
Common Radiator Noises and What They Mean
What it sounds like: Loud bangs, like someone hitting pipes with a hammer.
What causes it:
Expansion – Pipes expanding and contracting as they heat up
Kettling in system – Limescale or sludge causing water to boil
Pump over-speed – Circulation pump running too fast
Is it serious: Usually not dangerous but indicates a problem. Repeated loud banging can stress pipe joints over time.
Hissing Sound
What it sounds like: Continuous or intermittent hissing.
What causes it:
Air escaping – From a small leak or during bleeding
Faulty thermostatic valve – Valve not seating properly
Pressure too high – System over-pressurised
Is it serious: If hissing continues when the radiator is off, you may have a leak.
Gurgling or Bubbling
What it sounds like: Water bubbling or gurgling inside the radiator.
What causes it:
Air trapped in radiator – Most common cause
Air in pipes – Air moving through the heating system
Low water pressure – Not enough water circulating properly
Is it serious: Usually not serious. Often fixed by bleeding radiators and checking system pressure.
Quick fix: Bleed the radiator using a radiator key. If gurgling continues after bleeding, call an engineer.
Humming or Vibrating
What it sounds like: Continuous low humming or vibration.
What causes it:
Loose valve – Thermostatic or lockshield valve loose
Pump vibration – Transmitted through pipes to radiators
Water flow turbulence – High flow rate causing vibration
Is it serious: Usually just annoying rather than serious.
Quick fix: Tighten the valve nuts at each end of the radiator with a spanner. Don’t overtighten.
Trickling or Dripping
What it sounds like: Sound of water trickling inside radiator.
What causes it:
Normal circulation – Water flowing through radiator
Air pockets moving – Air working its way through system
Partial blockage – Sludge restricting flow
Is it serious: Normal trickling is fine. If radiator is cold at the bottom, you may have sludge buildup.
Need Help Diagnosing the Problem?
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We can often diagnose the problem over the phone and let you know if it needs a visit.
Call 0800 328 0449 nowWhen to Call an Engineer
Loud banging that won’t stop – After bleeding radiators and checking pressure.
Multiple radiators making noise – Indicates a system-wide problem.
Hissing with visible water – You may have a leak.
Cold radiators with gurgling – Likely needs power flushing.
Getting worse – Noises becoming louder or more frequent.
Winter Makes Radiator Problems More Obvious
During summer, radiators are off or running minimally. In winter, they run for hours every day, making any problems much more noticeable.
Small issues that were barely audible in autumn can become loud and annoying in the depths of winter.
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