Building Troubleshooting Forum

Boiler Making Strange Noise - Any Ideas?

Posted by John Doe on October 26, 2023, 10:35 AM

Hi everyone,

I've recently started hearing a strange noise coming from my boiler. It's not a constant sound, but it happens intermittently, usually when the heating is running. The noise is kind of a hissing or sometimes a gentle knocking sound. It's not excessively loud, but it's definitely new and concerning.

My boiler is about 5 years old, a brand named "ComfortHeat Model X". I haven't noticed any other issues with the heating system, like radiators not getting hot or pressure dropping, but I want to get this checked out before it becomes a bigger problem.

What I've noticed:

Intermittent hissing or gentle knocking sound.
Occurs when the heating system is active.
No obvious leaks or drops in system pressure.
Boiler seems to be heating water effectively otherwise.

Has anyone experienced something similar with their boiler? What could this noise indicate? I'm trying to gather some information before I call out a professional, to have a better understanding of what might be going on.

Any advice or suggestions would be greatly appreciated!

Thanks,

John Doe

Replies (3)

Posted by Sarah Brown on October 26, 2023, 11:15 AM

Hi John, a hissing sound can sometimes indicate a small air leak in the system or within the boiler itself. It could also be related to the pump or a valve.

My old boiler used to make a similar noise, and it turned out to be a small amount of air trapped in the heat exchanger. Bleeding the radiators helped, but eventually, a technician had to service it to fully resolve it.

The knocking sound could be a bit more concerning, possibly related to thermal expansion or a blockage. It's good you're looking into it!

Posted by Mike Peterson on October 26, 2023, 11:45 AM

John, I agree with Sarah. Hissing often points to air. You might want to try bleeding your radiators first if you haven't already. Just be sure to check the system pressure afterward, as it might drop.

For the knocking, could you describe it a bit more? Is it a sharp knock or a dull thud? Sometimes, this can be due to sediment build-up or scale in the pipes or boiler. A power flush might be necessary if that's the case.

Definitely get a qualified Gas Safe registered engineer to look at it.

Posted by Anna Kim on October 26, 2023, 12:30 PM

Hi John, my neighbour had a similar issue last winter. It turned out to be a faulty thermostat sensor causing the boiler to cycle on and off erratically, leading to some unusual noises. It's a long shot, but worth mentioning.

It's always best to err on the side of caution with boilers. A professional inspection will give you peace of mind.

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Boiler Making Strange Noise - Any Ideas?

What I've noticed:

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