| 摘要 |
Drainage pipes are made from synthetic resin, provided with openings in the walls for the water to enter and an outer layer of a filter medium attached to the walls of the pipe. The filter medium is attached to the outside and comprises several layers of a fibrous, flocculated or granular material. The pipe thus forms a single unit incorporating the filter medium which simplifies the laying of drainage by making it a single step operation easily carried out with mechanical equipment. |
