Prodn. of a drip feed irrigation pipe (1) consists of continuous extrusion of a plastic pipe (1) onto the inner wall of which are welded, at intervals, flow limiters or drippers (4) having a collection chamber facing the tube surface and connected to the inside of the pipe by a labyrinth channel. Contactless sensors (40), pref. capacitance detectors, detect the start or finish of a limiter and signal the operation of a unit to pierce the wall of the tube to connect the collection chamber to the outside. The piercing unit uses a laser (42) pref. of the Nd/YAG type with optical focussing (44).
