Are Hot Water Cylinders Noisy?

Hot water cylinders are generally quiet during normal operation, but they can make noticeable sounds under certain conditions. Common noises include hissing, gurgling, rumbling, and even banging. While occasional noise isn’t always a cause for concern, persistent or loud sounds often indicate an underlying issue.

One of the most common causes is sediment buildup inside the cylinder, especially in areas with hard water. As the heating element warms the water, it can cause trapped water beneath the sediment to boil, creating popping or rumbling noises. Flushing the cylinder regularly can reduce sediment and extend the life of the unit.

Other noises, like whistling or screeching, may signal a problem with valves—such as a faulty pressure relief valve—or issues with water flow. Tapping or knocking sounds might occur if pipes are not securely fastened or if the plumbing system is experiencing thermal expansion.

Newer cylinders tend to be quieter due to better insulation and improved technology, while older models may become noisier over time. If you notice new or worsening sounds, it's advisable to have the system checked by a qualified plumber. Early attention can prevent further damage and maintain the efficiency and safety of your hot water system.