Why is the water in the spare water tank still flowing downstairs when the hotel stops water supply?

Because if it's a public water tank. Then he usually stops cutting. When the water is cut off, his water can't flow down. The function of reverse logging. Only water can be used. And the water can't go back.

Check valve, also known as check valve, refers to the valve that automatically opens and closes the disc depending on the flow of the medium itself to prevent the medium from flowing backwards, also known as check valve, one-way valve, reverse flow valve and back pressure valve. Check valve is an automatic valve, its main function is to prevent the medium from flowing backwards, prevent the pump and driving motor from reversing, and release the medium in the container.