Central heating systems involve both moving and static parts, and the movement of water through the system is bound to cause some noise.
You’re most likely to hear noise once you turn your heating system on, but it should dissipate when things start to heat up. In cold weather, central heating pipes may also make noises as they expand and contract.
However, a consistently rattling radiator, or a rattle that keeps getting louder, should be checked out.
Here’s a guide to why your radiator is rattling and how to fix it.
What does a rattling radiator mean?
A rattling radiator is generally normal and is most likely caused by expansion and contraction of the metal after a heating or cooling of water which flows into it.
Radiators may rattle gently during normal use, but the noise shouldn’t be easily audible unless you’re nearby. If your radiator is making more of a hiss than a rattle, check out our article here.
Here are four situations in which you might encounter a rattling radiator:
1: If you’ve fitted a new radiator
If you’ve fitted a new radiator or valves and either are rattling, you should check whether it’s set up properly. If the rattling emanates from the valve or near the valve, check the calves to make sure they’re set up correctly.
There are two valves on most radiators - a smaller lockshield valve that doesn’t have a dial, and a larger TRV valve that has a dial with numbers.
Conventionally, the TRV valve is fitted on the flow side. To identify the flow side entering your radiator, switch your heating on and feel which pipe gets hot first - it should be the one on the TRV valve side.
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If the pipe on the TRV side doesn’t heat up first, then your TRV is fitted on the return pipe. Modern TRVs are usually bidirectional, meaning they can be fitted on the flow or the return. However, unless you bought the lockshield valve and TRV as a pair, it’s best practice to fit the TRV on the flow (and this is recommended in most situations anyway). Try swapping the valves, so the TRV is fitted on the flow and the lockshield on the return.
If you’ve fitted a new pump
If you’ve fitted a new pump, your pump may be set too high for your system. The new pump is possibly more powerful than the old one, regardless of whether it’s set the same.
Try adjusting your pump and turning it down. This will alleviate the rattle if the pump is the cause.
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How to make a radiator stop rattling?
If your heating system has been running well for a while but has recently developed a rattle, the first port of call is to bleed the radiators.
Over time, your central heating system may induct air through the cold water feed in the loft or possibly even from a leak in the piping, pump, radiators or valves. To remove excess air, you’ll need to bleed the radiator.
Radiator bleeding is easy, and it’s worth doing regardless of whether it’s the cause of the rattling.
To bleed a radiator:
- Switch your heating system off and allow it to cool.
- Find the bleed valve, it’s usually located in the top corner of the radiator.
- Place a towel under the radiator to catch any water.
- Use a bleed key or screwdriver to unscrew the bleed valve gently. Listen out for any hissing of air. Some water may drip out, but the aim is to release air and not water. Easy does it!
- After bleeding, check your boiler's pressure gauge. If you only bleed one radiator, it’s unlikely the bleeding process will have depressurised the system.
If you keep having to bleed your radiators, then it’s sensible to check the feed and expansion tank in the loft (for conventional heating systems only). Check that the ball valve is not stuck and that the water level is not below the level of the fill pipe. Both of these issues will cause the heating system to draw air into the system, resulting in sorts of problems, including rattling radiators.
How to fix a rattling radiator?
If bleeding fails to alleviate the rattle, try and find the exact source of the rattling noise. It may be coming from your radiators, valves or pipes.
If the noise is coming from the valves
Firstly, check the above section above on ‘if you’ve fitted a new radiator’.
Next, remove the cover of the TRV valve to reveal the valve pin protruding from the top. Your valve pin might be seized or very sticky, which is causing tension and vibrations in the valve. Push down on the valve with a screwdriver and ensure it springs back and forth readily.
Above: TRV Valve Pin
Your valve may also be clogged with sludge and debris. Isolate the radiator and disassemble the valve to check it for debris. Ask a heating engineer or plumber if you’re unsure.
If the noise is coming from the radiator itself
Providing bleeding doesn’t work, your radiator may be clogged with sludge and debris. This is especially likely with old radiators in conventional heating systems. Consider flushing the radiator - ask a plumber or heating engineer if you’re unsure. In addition, check the radiator side panels to make sure they’re not loose.
If the noise is coming from the pipes
When the rattle sound comes from the pipes going in and out of your radiator, the pipes might be vibrating against a backboard or another hard surface. Feel the pipes to see if they’re vibrating and place some fabric behind them if they’re making contact with another surface.
If the rattle has started happening recently, check your pump to ensure it isn’t set too high. Leaks or limescale may also cause rattling pipes - if you hear rattling noises coming from pipes inside the walls or floor, then it’s worth consulting a heating engineer or plumber.
If the noise is coming from somewhere else
When you can’t trace the rattling to any of the above, the noise may be radiating from your boiler. If so, it’s worth getting a heating engineer or plumber to check it out as soon as possible.
If the rattles are coming from the pump, check the pump settings and consider bleeding the pump. This is much the same process as bleeding a radiator - ask for professional advice if you’re not sure of what to do.
Summary: Why is my radiator rattling and how to fix it
Radiators may rattle gently during normal use, but it's worth diagnosing the fault if the rattle noise is getting louder or becoming a chronic issue. The source of the rattle is key here - it may emanate from the valves, pipes, radiator, or perhaps even the boiler or pump.
Bleeding the radiator may improve the problem, but if it returns, then that’s a surefire sign that your system is drawing in air from somewhere. Valves can also be the source of the rattle - they might be stuck or clogged. If the rattle is coming from inside the radiator, vibrating debris or sludge might be the issue.
If you’re unsure of what to do or can’t seem to fix the source of the rattle, get in touch with our experts to book an appointment.
Read our other guides on radiators
Fix your leaking radiator
Fix your cold Radiator
Fix your hissing Radiator
Fix your noisy boiler
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