What is a common cause of water hammer in plumbing systems?

Water hammer occurs when there is a sudden change in flow velocity, particularly in a plumbing system when valves are closed quickly. This rapid closure creates a shock wave that travels through the water in the pipes, leading to a loud banging noise and potential vibration.

The phenomenon is linked to the inertia of the moving water; when the moving water is abruptly stopped, it does not just cease instantly but instead creates pressure waves that can result in the characteristic sound and physical effects of water hammer. This is why proper valve operation and gradually closing valves can mitigate the occurrence of water hammer, helping to maintain stability within the plumbing system.

The other options address issues that can affect a plumbing system, but they don't directly relate to the dynamics that cause water hammer. Excessive pressure in pipes can lead to different problems, such as leaks or pipe failures, while low water levels in a tank might lead to insufficient water supply but do not specifically cause the shock waves characteristic of water hammer. Corrosion of pipes can degrade them over time, affecting their integrity and flow characteristics, but again, does not specifically lead to the sudden changes in flow that are the hallmark of water hammer.