Abstract: A modular assembly of channel sections (2) is disclosed which are connected to one another for providing a drainage system by a shutter coupling between a groove 24 formed at one end of any channel section and a rib (6') formed at the other end. Channel section (2) has a modular construction as it is provided with a number of parallel ribs (6') extending in a plane perpendicular to the length of the section at regular intervals so that the length of the final assembled channel can be changed by varying the coupling of the sections. Further anchoring ribs (6) are provided near ribs (6'). A shutter head member (26) coupled at either end of channel section (2) and having a dead but easily pierceable pipe fitting (30) is also provided.