What is water hammer primarily caused by?

Water hammer is primarily caused by sudden changes in the velocity of water flow within pipes, which can occur when a valve closes quickly. When a fast-closing valve abruptly stops the flow of water, the kinetic energy of the moving water generates a shock wave that travels back through the system. This phenomenon results in a noise and can cause physical vibrations or stress on the piping system.

In contrast, low water pressure does not contribute to water hammer, as it generally pertains to the force at which water is supplied and does not create the sudden pressure changes that lead to the hammer effect. Excessive use of fertilizers and poor irrigation design might lead to other issues in an irrigation system but do not directly cause water hammer. The key factor responsible for water hammer is the abrupt changes in flow velocity associated with the operation of valves, especially when they close quickly.