Guide To Boiler Kettling

Posted on: 12 April 2021

Kettling is an odd word that describes a common boiler problem. Knowing what it is, how to spot it, and what to do is important if you want to avoid damages and expensive repairs.


The most obvious symptom of a kettling issue is a deep rumbling sound from the boiler itself. The name kettling is apt because your boiler really will sound like a giant kettle that is about to burst or boil over. In a home, this noise will likely be heard throughout the building. In apartments or office blocks, you may have to be near the boiler to hear the rumble.

The boiler may also vibrate as it rumbles, which can increase the rumbling and even make it sound more alarming.


Hard water mineral scale buildup in the boiler is the usual culprit. Scale buildup restricts water flow and storage capacity, thus causing the water to overheat and boil instead of flow out of the boiler as it should. As the water boils, pressure mounts and you get the rumbling sound.

Issues with the thermostat can also lead to kettling. For example, if the thermostat is malfunctioning, the heating elements may overheat the water in the boiler, causing it to boil and begin to kettle.


The biggest danger is that the pressure that builds up from the boiling water will cause the boiler to burst with explosive force, which can damage your home or cause major injuries. Fortunately, this is rare.

It's much more likely that the heat exchanger will spring a leak, thus emptying the contents of the boiler tank all over the floor. You will end up needing extensive water damage repairs as well as major repairs for the boiler. In some cases, you may need to replace the boiler completely.


If you hear kettling from your boiler, you can avoid the worst of the dangers by acting quickly. First, cut power to the boiler so that the water can't continue to overheat. A boiler repair technician can then flush the boiler and clear out all of the mineral scale that has built up inside. They may also advise installing a water softener on the boiler inlet line.

If damage has occurred, either to the heat exchanger or the thermostat, then you may need to have these parts either repaired or replaced. Your technician will inspect the parts for you and make an informed recommendation.

Contact a boiler repair service in your area immediately if you suspect your boiler of kettling.