Ever sit there on the sofa surrounded by gurgling, humming, tapping and banging noises coming from the walls? Do you lie awake at night to the sound of a phantom kettle boiling?
There are two perfectly reasonable explanations: either your boiler is making strange noises, or your house is haunted. Neither option is ideal.
While we can’t advise you on any ghoulish ghostly goings-on, we do know a fair bit about plumbing, home heating, and peculiar boiler noises.
Hug’s Ultimate Guide to Strange Boiler Noises sets out all the weird and wonderful sounds you might be hearing from your boiler, what causes them, and practical steps on how to fix them.
Boiler noises – causes and fixes
When it gets into the swing of things, your boiler can pull out a whole repertoire from its back catalogue. But much like the top 40 nowadays, it can be hard to tell the difference between each noisethe different noises and understand exactly what they meaneach one means.
Here are a few of the most common weird boiler noises that could be offending your ears right now.
Gurgling
It’s quite normal for your boiler, pipes and central heating to make a small amount of gurgling or humming noise as it goes about its daily business. Gurgling which is loud and constant, however, is something which requires a bit more investigation.
Possible cause: Air trapped in the system
As your house and your system get older, parts of the supports start sagging or drooping slightly. Older radiators will naturally drop slightly to one side or the other.
This can change the ‘level’ of the radiators and the surfaces become uneven. When water is pumped into the system, air bubbles begin to form as it flows around the uneven surface. These pockets of trapped air begin to build up and cause the annoying gurgling noise.
Naturally, as houses age and hot water systems get older, parts of the supporting structures that hold everything in place start to sag or droop – It’s not uncommon for older radiators to drop slightly on one side.
This “sagging” changes the balance of your radiators, making them uneven, and creates areas inside the panels that are difficult to fill with hot water.
Picture a fish tank set on a slope, now picture trying to fill that tank, full to the brim, with water. It can’t be done. Sure enough, as the tank is filled, there will come a point where the tank can be filled no further and water will start to flow over its lowest edge.
That’s essentially what’s happening inside your radiators, except the whole thing is sealed and, hopefully, doesn’t contain any fish.
As water is pumped around the system, air bubbles begin to build up in these hard-to-reach areas and it’s these pockets of trapped air that cause the annoying gurgling noises.
How to fix gurgling noises
This is one the best boiler noises, because you probably won’t need to call an engineer out to fix it.
The most effective way of stopping the gurgling noises is to bleed the system. This is fairly straightforward, but you should contact a professional if you’re not confident doing it yourself.
All you need to do is:
- • Open all the radiator thermostats and put your heating on full-blast for 10 to 15 minutes.
- • Turn off the circulation pump and wait until the radiators and pipes have fully cooled down, which should take no more than an hour.
- • Use a bleed key or a screwdriver to drain the water into a container and repeat for each radiator.
- • Then turn the boiler back on and check the boiler pressure is at the correct level (see our guide to Boiler Pressure problems if you’re unsure what this should be)
If bleeding the radiators fails to stop the gurgling noises, there’s probably something wrong with the components of your central heating system and you’ll need to contact an engineer.
Whistling noise (AKA kettling)
Your boiler might be making a high-pitched whistling noise, a bit like one of those old-fashioned kettles. We geniuses in the central heating industry refer to this by its technical name: kettling.
Possible cause: Limescale build-up
If you live in an area with hard water, deposits of limescale can build around the heat exchanger – the bit where the boiler heats the water.
Hard water has a higher concentration of calcium salts. These are insoluble and end up sitting at the bottom of the exchanger, restricting the flow of water and trapping hot water in the exchanger.
This trapped water has nowhere to go, begins to boil and voila – there’s your whistling sound.
Other causes of kettling might be:
• Sludge deposits
• Faulty thermostats
• Incorrect settings
• Poor quality installation
How to fix whistling noises
First of all, relax!
A lot of people worry that kettling could lead to the boiler exploding. Boilers have a number of safety controls that will shut the boiler down when something critical happens and will be able to cope with the expansion in the system, no matter how alarming the sounds are.
Unfortunately there is no DIY fix for kettling – you need to get an engineer out.
There are a few things an engineer can do to fix kettling and prevent it from happening again in future:
• Replace the heat exchanger
• Fit a Magnabooster
• Powerflush the system
Vibrating noise
This can be one of the scariest noises your boiler makes. The cause and the fix, though, could be fairly simple. Excessive vibration or ‘whooshing’ doesn’t present any immediate danger, but it could cause a fair bit of damage if it’s left to get worse.
Possible cause: Flue blockage
If your boiler is making a vibrating noise it probably has something to do with the air intake. Something might be blocking it or preventing air from flowing freely in and out of the system, resulting in the whooshing noise.
How to fix vibrating noises
Check the flue – the pipe on the outside of your house which expels waste gas and condensation from the boiler system. Make sure there’s nothing blocking it, and wipe away any build-up of fluff or dust.
If the flue looks clear, then it’s probably a blockage in the air filter. A boiler air filter is just like the one you might find in a car or a vacuum. Most air filters can be easily detached, removed, cleaned and then re-attached, but you should get a professional round if you’re unsure about how to do this.
Also check the condensate pipe for any signs of blockage.
Buzzing noise
Maybe it sounds like there’s a bee trapped in there, or entire swarm of them. You might also be able to hear a high-pitched whining/whirring noise, either constant or intermittent.
Possible cause: Broken burner, worn-out pump, defective fans
Buzzing noises usually occur when vital components in the system are damaged or have succumbed to the perils of old age.
Boiler components are long-lasting and each part of the boiler system can tolerate a great deal of wear-and-tear, but the strain of pumping out hot water time and time again across decades will eventually take its toll.
How to fix buzzing noises
This one is a cause for concern which requires the attention of an engineer. It’s vital that the problem is diagnosed as soon as possible. A quick fix is needed, and only a trained professional can get to the root of the issue.
Are strange boiler noises dangerous?
If your boiler is making any of the noises we’ve mentioned above, there’s no need to panic.
Boilers and heating systems have a number of programs and checks in place to ensure that they are operating safely, even when things go wrong.
Boiler explosions can happen, but they are very, very rare. When things get critical most boilers will just shut down and go into hibernation.
It’s perfectly normal to be concerned about strange boiler noises, though.
Calling a trained professional out to diagnose the problem can provide you with some much needed reassurance and will make sure that any underlying issues are dealt with before they cause any further damage.
Should I replace my boiler if it makes strange noises?
Every boiler reaches the end of the line eventually, but we can be overly-zealous when it comes to replacing them.
Boilers have a long lifespan, and many of the issues we’ve highlighted here have easy fixes.
At the same time, installing a new boiler can cost less than a series of expensive repairs on a boiler which keeps breaking down.
Installing a new boiler also means you’ll probably be able to save on energy bills, with today’s installations tending to be far more cost-efficient than their 15-to-20-year-old brothers and sisters.
Above all, the decision comes down to one simple question – can you afford a new boiler right now? If the answer is no, you should squeeze as much life out of your current boiler as possible.
If you can’t afford a new boiler but the repairs are costing you an arm and a leg anyway, you might want to think about getting one on finance. You won’t have to take a huge, all-in-one-go financial hit, but you will have a new boiler which isn’t costing you a fortune in repair work.
If your current boiler is being a pain in the backside and seems to be on its last legs, and you can afford the cost of a new boiler installation, then go for it. You’ll have peace of mind – something you can’t really put a price on – and it will save you both time and money in the long term.
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