A water-tube is a type of boiler that uses water-filled tubes to generate steam. In this design, water circulates through the tubes, which are heated by combustion gases. This allows for efficient heat transfer and quick steam production, making water-tube boilers suitable for high-pressure applications. Water-tube boilers are commonly used in power plants and industrial settings due to their ability to handle large volumes of steam. They are often compared to fire-tube boilers, where combustion gases pass through tubes surrounded by water. The water-tube design generally offers better efficiency and safety in high-demand situations.