Air-negative pressure, that is, we often say that positive pressure turns to negative pressure, the process is cumbersome and the effect is not good, and it has been gradually eliminated. Water negative pressure is what we call water circulation pump. Similar to air negative pressure, it relies on the high-speed flow of water to generate negative pressure. Water negative pressure characteristics: complex structure, inconvenient maintenance after problems; large water consumption, due to pollutants in the water, can not be recycled, large investment and waste of water resources; negative pressure generated is limited, and the negative pressure cannot be adjusted.