Radiator making noise: gurgling, ticking, banging or whistling

Match the noise to the likely cause

The type of sound, and when it happens, narrows things down quickly. Listen with the heating just coming on, and again once it has been running for twenty minutes.

Gurgling: air in the radiator

Air collects at the top of radiators, especially after the system has been drained or topped up, or when a small leak has let air in. You hear it as water trickling through a partly empty radiator, and the radiator is often cooler at the top than the bottom.

Bleed the radiator with the heating off and the radiator cool, holding a cloth under the bleed valve until water rather than air comes out. Our guide on how to bleed a radiator walks through it. Then check the boiler pressure gauge, because bleeding lets pressure out and a sealed system may need topping up.

If one radiator needs bleeding every week or two, air is getting in or gas is forming inside the system. That is usually corrosion, a small leak or a problem with the pump position, and it is worth having looked at before the radiators start to rust from the inside.

Ticking and creaking: expansion

Copper and steel pipes grow slightly as they heat up and shrink as they cool. Where a pipe passes tightly through a notch in a joist, rubs against a floorboard or sits in a tight clip, that movement comes out as a tick, click or creak. It is often loudest at night when the house is quiet and the heating switches off.

It is a nuisance rather than a fault. The fix is to give the pipe room to move: easing a tight clip, adding a felt or plastic sleeve where it passes through timber, or lowering the flow temperature so the pipes do not expand as much. Our guide to heating pipes noisy at night covers how to find where the sound is coming from before anyone lifts floorboards.

Whistling or humming: a valve that is nearly closed

When most thermostatic radiator valves in the house have closed because rooms are warm, the pump is still pushing water round and it has to squeeze through the few valves that remain open. A valve that is only just open can whistle, hum or buzz.

Try opening the valve on the noisy radiator a little more, or turning another radiator on so the water has more places to go. If the lockshield valve, the one with the plain cap at the other end, has been closed down too far, it can whistle too. Our guide to the lockshield valve explains how to adjust it without upsetting the rest of the system, and the one on thermostatic radiator valve settings explains what the numbers mean.

If whistling comes back whenever the TRVs close, the system may need an automatic bypass valve, or the pump speed turning down. Both are jobs for a heating engineer.

Banging and knocking: the one to take seriously

A loud bang or repeated knocking from radiators or pipes while the boiler is firing is different. It usually means water is boiling or flashing to steam somewhere it should not, because it is not moving fast enough through the boiler's heat exchanger. The common causes are sludge and scale restricting flow, a failing pump, a stuck valve, or low system pressure.

Boiler kettling noises covers that sound in detail. If the banging is loud, is getting worse or comes with the boiler locking out, turn the heating off and get it checked. A boiler that is overheating will usually shut itself down on its safety thermostat, but repeated overheating shortens its life.

If radiators are banging and the boiler is also showing a fault code, leaking, or you smell gas, switch the boiler off. If you smell gas, open windows, leave the property and call the National Gas Emergency Service on 0800 111 999.

Rushing water: pump speed and flow

A constant rushing or whooshing through the radiators, even when there is no air, often means the pump is set faster than the system needs. Many older pumps have a speed switch that was left on its highest setting at installation. Too much flow is noisy and wastes electricity.

Adjusting the pump speed and balancing the radiators usually settles it. If the noise started after new radiators were fitted or pipework was changed, the system may simply need rebalancing. Radiator balancing or power flushing explains how to tell which one your system needs.

Signs the noise is part of a bigger problem

A noisy radiator is sometimes the first sign of a system that is struggling. Get it looked at if the noise comes with any of these:

• Radiators cold at the bottom but warm at the top, which suggests sludge.
• The boiler pressure dropping and needing regular top-ups.
• Black or rust-coloured water when you bleed a radiator.
• The boiler locking out, cycling on and off, or showing a fault code.
• Damp patches, drips or staining around radiator valves or pipework.

Getting a noisy heating system sorted

Loyal Plumbers covers London and everywhere inside the M25, 24 hours a day, with 10 vans on the road. Our engineers work on radiators, valves, pumps and whole heating systems, and gas work on the boiler is carried out by Gas Safe registered engineers. When you call 020 4652 8585, tell us which radiators are noisy, what the noise sounds like, when it happens and the reading on the boiler pressure gauge.

Our call-out charge is £60, and the engineer explains what they have found and what the fix involves before any work starts. You can read more about the work on our radiator repair and replacement and central heating pages.