The shaft, commonly known as the plastic "inspection shaft", is a drainage auxiliary structure set at the intersection of plastic drainage pipes, turning points, pipe diameter or slope changes, water drops or straight pipe sections at certain intervals to facilitate regular inspection, cleaning and dredging of pipes.

Hainan Most of the well seats of are molded by one-time injection molding, and the connection of changing pipe diameter and angle is achieved by reducing joints, angle changing joints, rubber sealing rings and other accessories. The plastic manhole is equipped with manhole cover, shaft and relevant accessories. The road load acts around the manhole through the manhole cover and well seat, avoiding the damage of road load to the manhole. The well seat has the function of floating up and down, which can actively adapt to the changes in the height of the road surface. At the same time, the shaft adopts a special shaft, which can cut the corresponding length according to the burial depth on the site, which is flexible and convenient. The connection between the shaft, inlet (outlet) water pipe and the shaft base adopts flexible socket connection with rubber seal ring or heat shrinkable sleeve connection, which can adapt to the angle change in a small range, and is convenient and fast for construction, with good sealing performance and anti leakage, which can effectively prevent the secondary pollution of groundwater. It is an environment-friendly and energy-saving building material.