How are ballast tanks installed below the waterline filled with seawater?

Ballast tanks are critical components of a ship's stability system, allowing it to adjust buoyancy and trim by managing weight distribution. The correct method for filling these tanks with seawater is by opening the main sea valve. This valve is connected to the ship's hull and allows seawater to flow directly into the ballast tanks when it is opened, effectively filling them.

When the main sea valve is operational, water pressure from the ocean can easily push seawater into the tanks, ensuring rapid and effective ballasting while the vessel is at sea. This method is efficient and minimizes the need for extra equipment or manual labor.

Although a pump system can also be used to fill ballast tanks, it is typically independent of the vessel's main access to seawater and may be used in different situations, such as pumping water out of the tanks rather than filling them directly from the sea. Manually pouring water into the tanks is impractical, especially on large vessels, since it would be time-consuming and require significant manual effort. Opening a ballast maintenance hatch would provide access to the tanks for inspection or maintenance rather than filling them, making it an inappropriate method for filling with seawater.