Which of the following can lead to water hammer in a plumbing system?

Water hammer is a phenomenon that occurs in plumbing systems when there is a sudden change in the flow of water. This is often the result of rapid valve closure. When a valve is closed quickly, the flowing water cannot stop immediately due to its inertia, leading to a shock wave traveling back through the pipe. This generates a loud banging noise and can cause stress on the plumbing system, potentially leading to pipe damage over time.

The other options do not contribute to the occurrence of water hammer. A stable pressure balance would maintain an even flow, preventing abrupt changes in pressure that could lead to water hammer. Steady flow rates imply a constant movement of water, which would not create the conditions necessary for a water hammer event. Low temperature, while it can affect some physical properties of the water, is not directly related to the dynamics that cause water hammer; it does not influence the flow pattern or pressure changes significantly enough to trigger this phenomenon.