Which device is specifically designed to allow waste to be unloaded from a holding tank?

The deck pump-out fitting is specifically designed to facilitate the unloading of waste from a holding tank. This fitting is typically located on the deck of a vessel and connects to the holding tank, allowing waste to be pumped out into a proper disposal system, such as a sewage treatment plant or a designated waste facility. The design ensures that liquids can be efficiently removed from the tank, promoting a sanitary environment and compliance with environmental regulations regarding waste disposal.

In contrast, seacocks are valves that control the flow of water into and out of a vessel, primarily serving as intakes for systems such as cooling and sanitation. A Y-valve is used in plumbing systems to control the direction of a fluid flow, allowing for the selection between two discharge options, but it does not provide a direct means to pump waste out of a holding tank. A siphon break is a device that prevents the backflow of water and protects the system from siphoning, but it does not facilitate waste removal from a holding tank. Thus, the deck pump-out fitting is the intended device for discharging waste from a vessel's holding tank.