Drip irrigation system

A drip irrigation system comprising a thin walled thermoplastic conduit for conducting irrigation liquid having formed integrally therewith an axially directed wall portion of increased thickness, outlet apertures formed in said wall portion in an axially spaced relationship, a plurality of discrete, substantially flat emitter units, respectively heat welded to axially spaced apart locations of an inner surface of said wall portion which locations respectively include said apertures, each emitter unit comprising a body member of a substantially rigid thermoplastic material which is heat sealable with respect to the conduit, said body member having a first portion thereof heat welded to one of said spaced apart inner surface locations in a juxtaposed relationship with an outlet aperture and having a second and opposite portion thereof with an elongated groove formed therein, a cover member juxtaposed with respect to said second portion and defining with said groove a flow restricting flowpath spaced and thermally shielded from said first portion, directed towards the interior of said conduit and located substantially in the flow direction of said conduit, emitter unit inlets serving respectively to effect communication between the conduit interior and the inlet portions of the flowpaths, and emitter unit outlets serving respectively to effect communication between adjacently formed outlet apertures of said conduit and the outlet portions of said flowpaths, and wherein said cover member is constituted by a resiliently flexible membrane formed of a natural or synthetic elastomeric material and displaceable toward and away from said flow restricting flowpath in accordance with flow pressure variations in said conduit so as to stabilise the output rate of said emitter unit with respect to said variations.