Last week we received a call from a regular customer who had an issue with their boiler but didn’t know the source of the problem. On the phone, he told me that there were rumbling and whistling noises coming from the boiler. I asked if it sounded like the noise from a kettle and they said that it did. I knew from this that their boiler was kettling.
They were wondering whether this was dangerous or not. I told them that sometimes it can be, but not often. Because they had spotted the noises early on, this boiler could be repaired and they did not need a full boiler replacement.
When I got to their house, I knew that the kettling was due to a build-up of sludge blocking the system. This raised the temperature of the water inside. The water inside your boiler should not boil. The speed at which the water passes through the flames prevents this from happening. So when there is a blockage in the system, the water moved along slowly and gets hotter than it should. As it starts to reach 100 degrees, it begins making noises similar to water boiling in a kettle – hence the name kettling. In this particular case, it was a build-up of magnetite – an iron-based chemical that wears of the insides of radiators. To solve the issue, I took apart the heat exchanger and scrubbed it clean. This cleared the blockage that the water flows through and the water was no longer heating too high.
After the job was completed, I filled the customers in on how getting a regular boiler service can stop the build-up of sludge and prevent kettling from happening.