Which of the following is an effect of hydraulic shock?

Hydraulic shock, commonly known as water hammer, occurs when there is a sudden change in the velocity of water flow, typically due to a valve closing rapidly or a quick change in direction of the flow. This sudden stop or change creates pressure waves that can result in significant forces being exerted throughout the plumbing system.

The correct response highlights that weakened joints and leaks can result from these pressure spikes associated with hydraulic shock. When the pressure wave travels through the piping system, it can impose stresses that exceed the mechanical limits of joints, fittings, and the pipes themselves. Over time, this can cause physical damage, leading to weakened connections and ultimately resulting in leaks, which compromises the integrity of the plumbing system.

Considering the other options, increased flow rate does not typically result from hydraulic shock; instead, the shock itself is often caused by sudden reductions in flow. Corrosion of valves can be a separate issue impacted by factors such as water chemistry and flow velocity, but it's not a direct result of hydraulic shock. Improved system efficiency would not be a consequence of hydraulic shock; rather, the unpredictable pressures can lead to inefficiencies and potential system failures.