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SPS Mechanical Inc. Blog

The Problem of Boiler Kettling

Is your boiler rumbling like an enormous, sinister tea kettle? If so, don’t worry. The system probably isn’t going to blow up or anything. However, it is experiencing a problem that will need to be dealt with if you want it to continue operating properly. Let’s take a look at kettling, what causes it, and what it can do to your system if it isn’t taken care of.


Boiler kettling is the result of lime scale buildup in the boiler’s heat exchanger. Lime scale is a kind of chalky mineral deposit, the result of hard water exposure over a long period of time. The lime scale in the heat exchanger restricts the flow of water through the pipe, causing it to start evaporating into steam. Water expands to over 1600 times its volume when it becomes steam, which puts an immense amount of pressure on the heat exchanger. This is what causes the rumbling sound, it’s the heat exchanger struggling to contain the steam buildup with no way to vent the pressure.

Problems Associated with Kettling

If the pressure on the heat exchanger isn’t relieved, it will eventually cause the heat exchanger to burst from the strain. Fortunately, most modern boilers are equipped to shut down the system before the problem gets that bad. If that happens, though, you’re still going to be stuck with a non-functional boiler. If you hear your boiler kettling, shut it down and call for repairs right away. The lime scale will need to be scraped out, and possibly the heat exchanger will need to be replaced. It depends entirely on how advanced the lime scale is.

SPS Mechanical Inc. offers boiler repair services throughout Haddonfield, NJ. If you need boiler repair services of any kind, call today to schedule an appointment with one of our experts.

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