A water tank related to a drainage device that operates using the siphon principle (without power) The liquid in the equipment needs to be discharged into a lower level pool. When the liquid level in the equipment is higher than that in the atmospheric leg pool, the liquid flows towards the pool through a long pipeline similar to the "atmospheric leg" under the action of gravity. There is no need for additional power to drive the liquid flow in the pipeline, and it can prevent gas from entering the equipment system, ensuring the normal operation and safety of the system.Material