Radiator Making Noise? What Each Sound Means

Updated July 2026 · Emergency Plumber Chelsea

Radiators get noisy at this time of year for a reason. After a summer switched off, air collects in the system, valves stiffen, and the pipes cool right down. The first few times the heating runs in autumn, the whole system expands, air moves around, and every sound seems louder in a quiet house at night. Some of those noises settle within a few days. Others are an early warning of a fault that is much easier to fix in October than on a freezing evening in January. Working out which is which starts with describing the sound.

Ticking, clicking and creaking are usually expansion. Steel radiators and copper pipes grow slightly as they heat up and shrink as they cool. Where a pipe passes through a notch in a joist, rubs against a floorboard, or is held tight in a clip, that movement makes a tick or a creak. You hear it most when the heating first comes on and again after it goes off. It is harmless. In Chelsea's period houses, with long pipe runs under suspended timber floors, it can be more noticeable than in a modern flat. If it bothers you, a plumber can ease the pipe where it rubs, fit a plastic clip or sleeve, or pack the notch, but that means lifting boards, so it is usually only worth doing if you are having other work done. If the clicking is coming from the boiler itself rather than the pipes, read our guide to a boiler clicking noise.

Gurgling, trickling and bubbling mean air. Air rises to the highest point, so it collects at the top of radiators and in the pipework on upper floors. You hear water trickling past it as the pump pushes water round, and you often find the radiator is cold across the top while the bottom is warm. The fix is to bleed it. Turn the heating off, let it cool, put a cloth under the bleed valve at the top corner and open it slowly with a radiator key until the hiss of air stops and water appears. Our step-by-step guide on how to bleed a radiator covers the order to work in.

Check the boiler pressure after bleeding. Letting air out also lets water out, and on a combi or system boiler the pressure gauge will drop. With the heating cold it should read around 1 to 1.5 bar, and if it has fallen below 1 bar you need to top it up through the filling loop. Low pressure can itself make a system noisy, because air is drawn in more easily and the pump struggles. Our guide on what pressure your boiler should be explains how to read and top up the gauge.

If a radiator keeps gurgling, air is getting in. Bleeding the same radiator every few days is a sign of a fault, not normal maintenance. On a sealed system, it often means there is a small leak somewhere and air is being drawn in as the pressure drops, or the automatic air vent on the boiler or pump is not working. On an older open-vented system with a tank in the loft, it can be a pump that is pumping over, pushing water up the vent pipe into the tank and pulling air in, often because the pump speed is set too high or the pipework is poorly arranged. Air in the system also produces hydrogen when it reacts with steel radiators, so a radiator that needs bleeding constantly is corroding from the inside, and that is worth having investigated.

Banging, knocking and clanking are more serious. A single thud when the heating comes on can be a pipe moving as it expands. Repeated banging while the heating is running is different. It often means water is being overheated in one spot and flashing to steam, then collapsing, which is the same process as kettling in a boiler. The usual cause is sludge or scale restricting the flow through a radiator or the boiler's heat exchanger. You may also find radiators that are cold at the bottom, a sign that sludge has settled there. Our guides to a radiator cold at the bottom and a boiler that is banging or gurgling explain what to look for.

Water hammer sounds similar but has a different cause. If the bang comes when someone turns off a tap, or when the washing machine or toilet cistern stops filling, the noise is on the water supply pipes, not the heating. The fast-moving water stops suddenly and the shock travels along the pipe, and it can sound as though it is coming from a radiator because the pipes run side by side. Our guide to water hammer and banging pipes covers that fault.

Whistling and humming usually come from the valves or the pump. A thermostatic radiator valve that is almost closed forces water through a tiny gap, and on some valves that produces a whistle or a hum, especially when the other radiators in the house have closed down and more flow is pushed through the last ones open. Turning the valve up a little often stops it. A TRV head that has been fitted the wrong way round, with the flow going through the valve in the opposite direction to the arrow on its body, can also chatter or hum. A continuous hum throughout the house when the heating is on can mean the pump speed is set too high. Our guide to a thermostatic radiator valve not working explains how the valve works.

Some noises should not wait. Call an engineer if banging is getting louder or more frequent, if you have to bleed radiators every few days, if the boiler pressure keeps falling or rising, if bleed valves release black water or a smell like rotten eggs, or if the boiler locks out while the radiators are noisy. Sludge that has built up over years may need a system clean, and an engineer will also check the pump, the air vents and the expansion vessel. Our radiator power flush and central heating repairs pages explain what that involves.

A few habits keep radiators quiet through the winter. Bleed any radiators that are cold at the top when you first put the heating on in autumn, then check the pressure. Turn each thermostatic valve to maximum and back a couple of times at the start and end of the heating season so the pins do not stick. Keep the system inhibitor topped up after any repair that drains water out, because inhibitor slows the corrosion that creates sludge and gas. Our guide on when to turn the heating on lists the other first-start checks.

If your radiators are still noisy after bleeding them, or the noise comes with cold spots, pressure problems or a boiler fault, Emergency Plumber Chelsea sends Gas Safe registered engineers across Chelsea, Knightsbridge, South Kensington, Sloane Square and Fulham. We find the cause, explain the options and agree the work before we start. There is no call-out fee on jobs over 3 hours. Call 020 3002 6667.

Quick tips

• Ticking and creaking as the heating warms up or cools down is expansion and is harmless.
• Gurgling means air: bleed the radiator with the heating off, then check the boiler pressure.
• Needing to bleed the same radiator every few days means air is getting in; get it checked.
• Repeated banging with cold-bottomed radiators usually means sludge restricting the flow.
• A whistling TRV often quietens if you turn it up slightly.

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