Hydraulic transients can result in the following physical phenomena.

High or low transient pressures—These can be applied to piping and joints in a fraction of a second and they often alternate from high to low and vice versa. High pressures resulting from the collapse of vapor pockets are analogous to cavitation in a pump: they primarily accelerate wear and tear, but they can burst a pipe by overcoming its surge-tolerance limit. Subatmospheric or even full-vacuum pressures can combine with overburden and groundwater pressures to collapse pipes by buckling failure. Groundwater can also be sucked into the piping.

High transient flows—These can result in significant degradation of water quality as deposits and rust are loosened and entrained at high velocities. This is aggravated whenever flows reverse direction during a transient event. High-velocity flows also exert forces at pipe bends.

Transient forces—Rapidly moving pressure pulses result in temporary, but very significant, transient forces at bends and other fittings, which can cause joints to move. Even for buried pipe, repeated deflections combined with pressure cycling can wear out joints and result in leakage or outright failure. Thrust blocks are typically sized for steady-state forces plus a safety factor—not transient forces—and typically resist thrust in only one direction. In pump stations, low pressures on the downstream side of a slow-closing check valve may result in a very fast closure known as valve slam. A 10 psi (69 kPa) pressure differential across the face of a 16 in. (400 mm) valve can result in impact forces in excess of 2,000 lb. (8,900 N).

Column separation—Water columns typically separate at abrupt changes in profile or local high points due to subatmospheric pressure. The space between the water columns is filled either by the formation of vapor (e.g., steam at ambient temperature) or air, if it is admitted to the pipeline through a valve. With vaporous cavitation, a vapor pocket forms and then collapses when the pipeline pressure increases as more flow enters the region than leaves it. Collapse of the vapor pocket can cause a dramatic high-pressure transient if the water column rejoins very rapidly, which can, in turn, cause the pipeline to rupture. Vaporous cavitation can also result in pipe flexure that damages pipe linings. High pressures can also result when air is expelled rapidly from a pipeline, which tends to repeat more times than when a vapor pocket collapses.

Vibrations—Rapid transient pressure fluctuations can result in vibrations or resonance that can cause even flanged pipes and fittings (bend and elbows) to dislodge, resulting in a leak or rupture. In fact, the cavitation that commonly occurs with water hammer can—as the phenomenon's name implies—release energy that sounds like someone pounding on the pipe with a hammer.

Hydraulic transient impacts can be expected at the following locations:

Hydraulic transient impacts can be expected to occur at the following times:

Environmental concerns due to hydraulic transients include:

Hydraulic transients can result in the following infrastructure management issues and risks: