What are the Typical Causes of a Noisy Boiler?

February 10, 2015

A noisy boiler can be both annoying and alarming. Boilers are supposed to do their jobs quietly by providing steam or hot water for your heating system. So, when you hear yours gurgling, bubbling or rumbling, you should take action. These noises are usually a sign your boiler needs some maintenance work performed.


If you have hard water in your area, your boiler is likely developing layers of limey scale. If this isn't treated, the condition can worsen as mineral deposits increase the temperature needed for heat exchange. Hot spots with temperatures higher than the boiler's boiling point of 180 degrees can form over the rough surface of the deposits. The differing temperature between these hot spots and the other water in your tank can cause an eruption of air bubbles in the water, rising into the cooler waters of the tank, and then collapsing with a loud noise. This bubbling is also known as kettling. The result is less heating efficiency and higher utility bills. A service professional can chemically descale your boiler.

Water Temperature 

When a thermostat malfunctions, your burner may cause water to overheat and boil loudly. Lowering your thermostat should eliminate the noise, but it can also lower heat output. Overheating and bubbling may also be caused by contaminants in the water. These contaminants can cause foaming and impede contact between water and boiler tubes, resulting in overheating.

Air Leaks

Air trapped in your boiler system can lead to noises in pipes and radiators. Malfunctioning valves on the expansion tank or breaches in pipes and connections can let air into your system. Bleeding the valves to let out the air will help, but breaches and valves should be fixed.

Water Supply

When water pressure is low or the tank's water supply is inadequate, the heat in your boiler dissipates too slowly, resulting in boiling and kettling. The causes of this problem are usually faulty valves, frozen pipes. incorrectly sized pipes or wrong flow-rate settings.

For more information on what to do about a noisy boiler, contact Lozier Heating & Cooling. We've been serving Central Iowa since 1906. Our goal is to help educate our customers in the greater Des Moines, Iowa area about energy and home comfort issues (specific to HVAC systems). Credit/Copyright Attribution: "Johan Larson/Shutterstock"