What ship system is used to move water in and out of special tanks to control the vessel's draft, trim, and stability?

The ship system used to move water in and out of special tanks to control the vessel's draft, trim, and stability is the Ballast System. This system comprises a network of dedicated ballast tanks, pumps, piping, and valves. Its primary function is to manage the intake, storage, and discharge of ballast water, which is water intentionally taken aboard a vessel to ensure its safe and efficient operation.

Draft is the vertical distance from the waterline to the lowest point of the ship's hull. The Ballast System controls draft by adding or removing ballast water, effectively making the vessel sit deeper or higher in the water. For instance, a ship often takes on ballast water when empty to ensure proper propeller immersion and maintain a suitable freeboard.

Trim refers to the difference between the forward and aft drafts, indicating the ship's longitudinal inclination relative to the water. By moving ballast water between tanks located at the bow (front) and stern (back) of the ship, the Ballast System can adjust the vessel's trim, balancing it to optimize speed, reduce resistance, or improve handling.

Stability is a vessel's ability to return to an upright position after being inclined or rolled by external forces like waves or wind. The Ballast System enhances stability by lowering the ship's center of gravity through the strategic placement of ballast water, particularly in lower tanks. This makes the vessel more resistant to rolling and less prone to capsizing.

Within the system, pumps are mechanical devices used to draw water from the sea into the ballast tanks or to discharge it from the tanks back into the sea. The piping forms the network of tubes through which this water flows, while valves are crucial control devices that regulate the direction and amount of water entering or leaving specific tanks, allowing for precise adjustments to the vessel's draft, trim, and stability.