These can be used as extension pipes to screen pipe. They are of two types :
- C. S. Pipe: For shallow-depth (up to 80 m) red colour code.
- C. M. Pipe: For medium-depth (up to 250 m) yellow colour code
These pipes may be plain or ribbed. They have transverse slots and are mainly used in bore wells, from the water-table Level onwards.
Ribbed Screen Pipes
These pipes have longitudinal ribs and transverse slots. The ribs keep granulated soil away from the slots, and increase the permeability rating to more than double when compared to plain screen pipes.