A deep, sustained sound from the boiler when it's running on low rate, with vibrations you can feel through the floor or walls. Don't worry. Your boiler probably doesn't need replacing. It's almost always a dirty injector, and it's usually fixed during an annual service.
What does a trumpet noise sound like?
It's a low-pitched, sustained noise. Not a quick rattle, not a kettle whistle. More like a brass instrument being held on a single note. Sometimes it comes with a distinct vibration that travels through the wall the boiler is mounted on, or through the floor below.
Most owners notice it when the boiler is running steadily on low rate, for example during long radiator-only heating cycles in mild weather, rather than when the boiler is firing hard for a hot tap.
What causes it
The most common cause on Ideal Logic boilers is a dirty injector. The injector is the small jet that sprays gas into the burner where it ignites. Over time, carbon and debris build up around the injector, partially blocking it. The restricted gas flow changes the way the gas mixes with air at the burner, and that change is what produces the trumpeting noise and the vibration.
Other causes worth considering, though less common:
- Limescale on the heat exchanger, which can also cause a kettling or rumbling sound (different to the steady trumpet, but sometimes confused with it)
- Loose flue components resonating with the burner
- Pipework not properly clipped behind the boiler, allowing pipes to vibrate against the wall
If the noise is more of a high-pitched whistle or whine rather than a low trumpet, the cause is usually different (often a faulty gas valve). Different symptom, different fix.
Don't replace the boiler over this. A trumpet noise is rarely a sign of a serious problem. Online forum advice that suggests "noisy boiler equals dying boiler" is wrong in this case. A dirty injector is a service-level fix, not a replacement-level fault.
What to do about it
Book a service if you're due one
The injectors are inspected and cleaned as part of a standard annual boiler service. If you haven't had your boiler serviced in the last 12 months, booking the service usually solves the trumpet noise as a side-effect of the routine work. You also get the warranty-protecting paperwork that the manufacturer requires for the warranty to remain valid.
Book a repair if a service was recent
If you've had a service within the last few months and the trumpet noise has come back, book a separate diagnostic visit. Either the injectors have got dirty unusually fast (which can suggest a wider system issue, like a contaminated gas supply or a misadjusted burner), or the noise is being caused by something other than the injectors. A diagnostic visit is covered by the £99 call-out.
Don't wait too long
A trumpet noise on its own isn't dangerous. But it's a sign the boiler isn't burning the gas as cleanly as it should, which over time can contribute to other issues such as flame failure faults or reduced efficiency. Sooner is better than later.
Related advice
If you're not sure whether the noise you're hearing is a trumpet or something else, our boiler repairs page covers the common boiler noises and what each usually means. If you're wondering whether your annual service is due, our servicing page covers what's included and the typical price.
