Category - Boilers
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Will Scholfield, Engineer

12 May : Updated 17 Apr ● 5 min read

Why is my radiator whistling?

You're going about your day when suddenly you start hearing a noise coming from your radiator. Radiator whistling can be both annoying and concerning, but understanding the common causes and solutions can help you restore peace and quiet to your home.

In this guide, our central heating experts will be looking at the reasons why your radiator is whistling and what you can do to fix it.

What causes a radiator to whistle?

When hot water is transported to the radiator from the boiler through your central heating system’s pipework, it warms up the cold metal causing it to expand. This expansion process can cause a clicking sound, but this doesn’t necessarily indicate that there might be a problem.

If, however, you start noticing a whistling sound, it’s likely a sign that there might be a problem that needs addressing.

What problems can radiator whistling indicate?

A high-pitched hissing sound which may be similar to that of an old-fashioned kettle, can indicate the following problems: 

  1. There is magnetite and sludge build-up in your radiators.
  2. Your water flow rate is too high.
  3. The drain valve is open.

How do I stop my radiator from whistling?

We’ve compiled a list of some radiator whistling remedies to help try and alleviate the problem. However, if you’re not sure, please don’t hesitate to call on an expert to take a look.

How to bleed your radiators to combat whistling

Your first instinct upon hearing this noise should be to bleed your radiators.

Radiator bleeding requires  you to let some trapped air out from the valve to reduce any clicking and ticking sounds. For more advice, read our step-by-step guide on how to bleed your radiators for all the instructions you’ll need to do the job correctly.

Other ways to stop your radiators whistling

If you find that bleeding your radiators doesn’t stop them from making a whistling or hissing sound then further investigation will be required, ideally by a plumber or registered Gas Safe engineer.

The way to fix your radiator will be different depending on the cause, which is why we'll walk you through each possible solution.

Radiator whistling potential causes and solutions:

  • Limescale hotspots: A radiator that has limescale is likely to cause overheating and will need a boiler filter installed to help reduce the effects of limescale. You can also opt to have a system flush and clean out your radiator and heating system, though this may be more time-consuming.
  • High water flow rate: If your water flow rate is too high, turn your radiator valve to its maximum temperature setting. Raising your temperature to the highest level will allow your water to flow better. Turn it back down once the whistling stops.
  • Drain valves: The drain valve can sometimes be left open slightly after being used. If this is the case, try twisting the valves anticlockwise so that they are fully screwed on properly.

If you’ve tried these remedies and the noise persists, then you should reach out for help from a registered Gas Safe engineer. Limescale build-up, in particular, can cause a lot of problems for you and your home’s central heating system, so it’s crucial to get these addressed as soon as possible. 

How to prevent my radiators from whistling?

The best way to avoid problems with your radiators is by keeping your whole central heating system properly maintained year-round. More often than not, you can prevent issues from arising in the first place by taking good care of your boiler, as per the manufacturer’s recommendations. 

There are two devices that can be used to reduce and prevent limescale build-up (which, as we know, is one of the main reasons for boiler faults or breakdowns) -  scale reducers and water softeners. Let’s take a look at each of these:

1. Scale reducers

Magnetic scale reducers transform calcium crystals into smaller particles so that the water can pass through without the minerals sticking to the pipe. These are effective for around ten years, though you must make sure the reducer coincides with your warranty guarantee.  

Electrolytic scale reducers, on the other hand, generate a current between the cathode and anode. It breaks down the iron in the water and restructures the minerals to protect your pipework from limescale.

2. Water softeners 

When water flows to your boiler’s tank, there is an ‘ion exchange’ between calcium, magnesium, iron and sodium. The water softener will filter out these minerals using magnet-like resin beads and generate clean water for your radiators and pipes. This allows for a much more efficient means of preventing your radiator and pipes from experiencing limescale issues. 

You may even find that the manufacturer’s warranty is only valid if the boiler is fitted with a magnetic filter. Make sure you read through all of the documentation supplied with your boiler at the point of purchase so you don’t run the risk of invalidating any warranty periods.


Frequently asked questions

Still having radiator issues?

If your radiators are still whistling away after trying the fixes mentioned above, it may be time to get professional help from someone with the experience needed to investigate further.

At BOXT, we're here to make heating your home as easy and stress-free as possible, which is why our friendly team is on hand to offer expert advice right when you need it most.

Via our Live Chat you’ll be able to speak directly with one of our engineers who can work to help you through any radiator-related problems.

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