What component allows waste and soil to exit the ship's piping system?

The component that allows waste and soil to exit the ship's piping system is the scupper valve. Scupper valves are specifically designed as drainage systems that permit water and waste to flow out of a vessel, particularly from decks or other areas where liquid accumulates. They function by opening to allow the discharge of unwanted fluids, while preventing backflow of sea water into the ship. This is critical for maintaining the overall balance and cleanliness of the vessel.

The other components mentioned serve different functions: the drain valve is typically used for specific drainage purposes but is more common in systems where controlled drainage is required, not for general wastewater removal from the ship. The overflow outlet acts primarily to prevent overflow from specific tanks or compartments, and the inspection port is meant for access and visibility into the system, not for discharge purposes. Thus, the scupper valve is the most appropriate answer for facilitating the exit of waste and soil through the piping system on a ship.