What can cause water hammer in a hot water system?

Water hammer is a phenomenon that occurs in plumbing systems, characterized by a loud banging or knocking sound when water flow is suddenly stopped or changed. The correct response regarding the cause of water hammer is the sudden stop of flowing water.

When water flows through pipes and is abruptly halted, it creates a shock wave that travels through the water in the pipes. This shock wave can cause the pipes themselves to vibrate and resonate, leading to the characteristic banging noise. The pressure changes can also lead to potential damage to the plumbing system over time due to the stress created by these rapid changes in momentum.

In contrast, the other options relate to different aspects of water flow or supply but do not directly contribute to the mechanism of water hammer. A sudden change in water temperature can affect the thermal expansion and contraction of pipes but is not a primary cause of water hammer. Insufficient water pressure can cause issues with flow but does not directly relate to the sudden stop of water. Continuous water flow is the opposite of the situation that causes water hammer, as it implies there is no interruption in movement to create the pressure spike. Understanding these dynamics is essential for addressing and preventing water hammer in hot water systems.