30 centimeters. Ductile iron pipe has good oxygen resistance. The short pipe length of nodular cast iron disk bearing is 30 cm, which can effectively delay the corrosion of metal parts in the system, prolong the service life of metal parts and reduce the scaling of pipeline system. Dish-type bearing short pipe plays the role of changing the straight pipe interface of ductile iron pipe, and the straight pipe can be changed into socket or flange interface to change the connection mode. Ductile iron pipes are sockets, which can only be installed in sequence, and valves and water meters cannot be installed in the middle.