According to feng shui theory, it is not good to have a well behind the house, and there can be no water behind it. Since ancient times, the last stop has said that you are in the Jedi. Whether it is a dry well, a tap or a water storage well, water is the theory in geomantic omen. "Dragons are born in water", and Qinglong is on the left. Therefore, according to the position of the four beasts, water can not occupy Xuanwu, but only occupy the left side of the house, and it should be firmly buried.