Abstract: A drip irrigation system comprising a thin walled thermoplastic conduit having an axially directed thick wall portion, discrete, substantially flat emitter units being heat welded to axial spaced apart locations of an inner surface of said thick wall portion adjacent outlet apertures formed in said thick wall portion, the emitter units being preferably provided with an elastomeric membrane exposed to the throughflow pressure in the conduit for the purpose of stabilizing the output rate of each emitter unit vis-a-vis possible flow pressure variations in the conduit.