What is the primary cause of water hammer in a pipeline?

The primary cause of water hammer in a pipeline is a rapid increase or decrease in water flow. Water hammer occurs when the flow of water in a pipe is suddenly changed, typically due to a valve closing quickly or a pump that is turned off abruptly. This abrupt change creates pressure waves that travel through the water and the pipe, leading to strong vibrations and, often, noise.

When the flow of water is instantly halted, the momentum of the moving water causes a pressure spike that can result in the characteristic "hammering" sound. Over time, this pressure surge can also cause damage to pipes and fittings if it occurs frequently or with enough force.

While surges from temperature fluctuations can affect water pressure and operation, they are not the direct cause of the sudden pressure changes associated with water hammer. Corrosion damage can also weaken pipes but does not lead directly to the water hammer effect. Pumping too much water might contribute to other issues in a system but is not inherently tied to the rapid changes in flow needed to cause water hammer.