Abstract: A sub-soil drainage pipe segment 12 comprises a first round cylindrical portion 14 forming a socket 16 and a second round cylindrical portion 18 integral with and extending from the first portion, the inside diameter of the first portion being substantially equal to the outside diameter of the second portion. In the second portion there are a plurality of circumferentially spaced, longitudinally extending slots 22. The slots are defined by longitudinally extending side walls which diverge from the outside inwardly. A plain end 20 of the second portion forms a spigot which is receivable in the socket of a similar segment, so that a number of such segments can be interconnected end-to-end to form a sub-soil drainage line.