Why is My Radiator Tapping? Reasons & When It Needs Fixing

A tapping radiator is one of those noises that’s easy to ignore at first… until it keeps happening. Sometimes it’s gentle and occasional. Other times it sounds like someone flicking the pipe with a spoon — usually right when you’re trying to sleep.

The good news? Radiator tapping is rarely dangerous. In most UK homes it’s caused by normal movement in the heating system, not a failing boiler. But where and when the tapping happens matters, and it can tell you exactly what’s going on.

Let’s break it down properly.

What a radiator tapping noise actually is

Most radiator tapping noises come from metal expanding and contracting as it heats up and cools down.

When hot water flows into cold pipes or radiators:

• The metal expands slightly

• Pipes shift against clips, floorboards or walls

• You hear tapping, clicking or ticking sounds

This is completely normal physics — but poor installation, tight pipework, or small faults can make it louder and more frequent than it should be.

Radiator tapping when the heating turns on

This is the most common situation.

Why it happens

When the boiler fires up, hot water rushes into cold pipes and radiators. If pipework is tight where it passes through:

• Floor joists

• Wall plates

• Radiator brackets

…the expansion causes the pipe to “catch” and release suddenly, creating a tapping or ticking sound.

Typical signs

• Tapping starts shortly after heating turns on

• Noise fades once radiators are fully hot

• More noticeable in colder weather

Is it serious?

No. It’s annoying, not dangerous.

What helps

• Slightly loosening radiator brackets

• Adding pipe sleeves where pipes pass through wood

• Turning flow temperature down a little (if possible)

Radiator tapping when the heating turns off

This one catches people out.

Why it happens

When heating switches off, everything cools and contracts — essentially the reverse of warm-up tapping.

As pipes shrink back:

• They slide in clips or holes

• Stress releases in small jumps

• You hear tapping or clicking

Typical signs

• Noise starts 10–30 minutes after heating shuts off

• Tapping may travel along walls or floors

• Stops once system fully cools

Is it a fault?

No — it’s normal contraction noise, just louder in some homes.

Radiator tapping at night (the most annoying one)

If your radiator taps mostly at night, you’re not imagining things.

Why it’s worse at night

• The house is quieter

• Outdoor temperatures drop

• Heating cycles on and off more sharply

• Pipes cool faster

Small movements that go unnoticed in the daytime suddenly sound very loud at 2am.

Extra causes at night

• Thermostatic radiator valves (TRVs) reacting to cooler air

• Boiler anti-freeze or pump protection cycles

• Pressure changes as system cools

What helps

• Slightly lowering overnight flow temperature

• Making sure TRVs aren’t boxed in or covered

• Checking radiator brackets aren’t overly tight

Radiator tapping when the heating is off

If the heating has been off for hours and the radiator still taps, the cause is usually pressure or residual movement, not heat.

Common reasons

• Pipes cooling unevenly across the house

• Pressure equalising in the system

• Expansion vessel pressure issues (less common)

If the noise is occasional and stops on its own, it’s rarely a concern.

Radiator tapping only on one radiator

When just one radiator taps, it’s usually local.

Likely causes

• Radiator not sitting square on brackets

• Pipes slightly misaligned

• Lockshield valve too tight

• TRV reacting sharply to temperature changes

Easy checks

• Make sure radiator is level

• Gently loosen mounting brackets (don’t remove them)

• Check valves aren’t overtightened

Tapping vs banging vs knocking (important difference)

Not all noises are equal.

• Tapping / ticking → expansion, usually harmless

• Banging / clunking → possible sludge, air, or pump issues

• Hammering → water hammer or valve problems

If the noise is loud, violent or shaking pipes, that’s when you stop DIY checks and call an engineer.

Can air or sludge cause tapping?

Yes — indirectly.

Trapped air

Air pockets can cause uneven heating, making parts of the radiator expand faster than others.

Bleeding the radiator often reduces noise.

Sludge

Sludge restricts flow, causing temperature differences inside the radiator. That uneven heating can amplify tapping sounds.

If the radiator is also:

• Cold at the bottom

• Slow to heat

• Noisy in multiple ways

…it’s worth investigating further.

When radiator tapping is worth worrying about

Call a heating engineer if:

• Tapping turns into loud banging or knocking

• Noise is accompanied by cold radiators

• Boiler pressure keeps dropping

• Radiators vibrate or move

• Noise suddenly appears after plumbing work

A qualified heating engineer (often registered with the Gas Safe Register if gas-related work is involved) can quickly tell whether it’s harmless expansion or something deeper.

Can tapping increase heating bills?

Indirectly, yes.

If tapping is caused by:

• Poor circulation

• Tight valves

• Sludge buildup

…the system may run longer to heat rooms evenly. Fixing the root cause can quietly improve efficiency and comfort.

The short version (so you can sleep)

Most radiator tapping:

• Is caused by metal expanding and contracting

• Is more noticeable at night

• Is annoying but not dangerous

If your radiator:

• Heats properly

• Doesn’t leak

• Isn’t banging violently

…you’re almost certainly dealing with a normal system noise, not a failure.