What causes water hammer in plumbing systems?

Water hammer is primarily caused by sudden changes in water flow velocity, which often occur when valves are closed quickly. When a valve is abruptly shut, the moving water has no place to go, leading to a sudden stop. This change in momentum creates pressure waves that can result in a loud banging noise, known as water hammer. The pressure fluctuations can also cause stress and potential damage to the plumbing system.

In contrast, increased pressure from the water source does not directly cause water hammer; rather, it describes a general condition of the system. Corrosion in pipes may lead to blockages but is not a direct trigger for the hammering effect. Similarly, while ice formation in pipes can cause issues like freezing and can lead to bursts, it does not contribute to the specific phenomenon of water hammer, which is characterized by rapid changes in kinetic energy from water movement.