What device is installed on the line to prevent water hammer caused by a quick closing valve?

The correct choice identifies the water hammer adapter as the device specifically designed to mitigate the effects of water hammer caused by rapidly closing valves. Water hammer is a pressure surge that occurs when a fluid in motion is forced to stop or change direction suddenly, resulting in shock waves that can lead to significant damage in piping systems.

A water hammer adapter typically functions by absorbing the shock of the sudden change in fluid momentum, thus preventing abrupt pressure changes and protecting the piping and fixtures downstream from potential damage. The device can also facilitate gradual pressure transitions, further reducing the risk of water hammer.

In contrast, while a pressure regulator manages the pressure within a system and a relief valve prevents overpressure, neither specifically addresses the rapid pressure transients that occur during quick valve closures. A check valve helps prevent backflow in a piping system but does not serve to alleviate the shock waves associated with water hammer.