The Problem with Boiler Kettling

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If your boiler is making a deep, ominous rumbling sound, don’t worry. You’re boiler is probably not going to explode. It is, however, afflicted with a serious issue that needs to be dealt with before the system breaks down entirely. That problem is called kettling, and it can cause quite a bit of trouble if it isn’t dealt with as quickly as possible. Read on to find out how kettling happens, and what you need to do about it.


Hard water is water with a high calcium and magnesium content. While it isn’t dangerous to you, it can cause all sorts of havoc with any appliances that deal with water. Basically, long term exposure to hard water causes the formation of a chalky deposit called lime scale. Lime scale can build up in your heat exchanger, which restricts the flow of water through the pipe. This causes the water to start to boil and evaporate inside the heat exchanger.

As counterintuitive as it may seem, most residential boilers aren’t actually supposed to boil water. As the water in the heat exchanger evaporates, it expands about 1600 times over. This places an immense amount of pressure on the heat exchanger, which it isn’t equipped to deal with. That’s what causes the deep rumbling sound coming from your boiler.


If left unchecked for long enough, the added pressure on the heat exchanger can actually cause it to burst. However, most modern boilers are equipped with safety features that will shut down the system before it gets that far. Still, if you want to get your boiler back into healthy working order you should call for repairs as soon as you notice this happening.

Bell Plumbing and Heating offers comprehensive boiler repair services for its customers throughout Denver, CO. Call today to schedule an appointment.

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