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How To Identify Common Boiler Noises

Even though it’s the spooky season, homeowners shouldn’t have to deal with scary, unexplained noises coming from their boiler. Banging, rattling, and humming might be ok for a haunted house, but knowing the common causes of this boiler noises can help anyone decide what to do when they happen.

Banging Noises

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One of the most concerning noises for any homeowner is a loud, unexplained banging noise that happens in the home. Noises like that just sound dangerous, right? But are they?

The key to the answer to that question is the type of banging that is happening. If a single bang occurs as the boiler fires up, a likely culprit is a delayed ignition. If the boiler continues to make a repeated banging or popping noises the entire time it is running, it could instead be due to an issue known as “kettling.”

Kettling is essential when the part that actually heats the water up, known as the heat exchanger, is too hot. The banging noise is the result of the bubbles caused by the steam (created by contact with a too hot heat exchanger), reaching colder water and bursting. Kettling is caused by one of a few different problems - limescale deposits, too low water pressure, a malfunctioning thermostat, or simply having the water temperature set too high.

Rattling Noises

Rattling noises coming from the boiler are often related to having extra air in the pipes. Luckily, this can be a fairly easy fix, especially for a licensed technician, that just involves bleeding the extra air out. This should not be attempted by an untrained homeowner, though, as it can be potentially dangerous. 

In some cases, the rattling may be a loose valve or bolts. For homeowners who feel comfortable, the boiler should be checked for valves that need tightening, pipes that need clipping, or even faulty pumps. This is best performed by a licensed professional, however, as they can better identify the problem as well as being able to fix it quickly. 

Humming Noises

Suppose the boiler has started making loud, persistent humming noises. In that case, it is likely due to one of three different potential causes - loose components, too high of pressure in the system, or a circulating pump that has been set too fast. 


The most common cause of a humming noise from the boiler is a vibration that is caused by loose components, often brackets. It may also be caused by an open panel on the boiler or vibration of the actual boiler unit itself. 

Boiler pressure can also be to blame for a sudden humming noise. The average pressure for a boiler should be below 15 PSI (at the absolute most). Anything over that can cause the entire system to vibrate. The pressure gauge is usually either on the boiler’s front panel or on the side. 

When the circulating pump is set too fast, it can also lead to humming noises. There should be an adjustable dial located on the front of the pump. Start by turning the speed down, and see if that affects the noise. Homeowners who are unsure how to do this should contact a professional.

About Laney's Inc.

Laney’s Inc. opened in 1960 in Fargo, North Dakota. They are a one-stop resource for plumbing, electrical, and HVAC services 24 hours a day, 7 days a week. Laney’s Inc. also loves to give back to their local community by supporting local non-profits. The next time you need quality plumbing services in Fargo, call Laney’s Inc. right away!