BoilerFaultCodesYour boiler is likely suffering from a build-up of limescale or sludge inside the heat exchanger, causing it to vibrate or 'kettle' like a noisy tea kettle.
This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.
Technical description: Excessive burner noise, rumbling noises
What causes this fault?
This issue occurs when debris like magnetite or limescale builds up inside the main heat exchanger, narrowing the channels where water flows. Because the water cannot circulate freely, it begins to boil rapidly and turn into steam bubbles, which creates the loud rumbling or 'kettling' noises you are hearing. Over time, this restricted flow puts extra strain on the pump and reduces the efficiency of your heating.
This problem often becomes more noticeable in autumn and winter when the boiler is under high demand and the burner stays on for longer periods.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like None — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Worcester Bosch 29 HE Conventional is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.