Abstract

An irrigation emitter tube having, when free of pressure a pair of wall portions, one wall portion being essentially flat between its margins, the other also being essentially flat except for an outwardly arched longitudinally extending portion, the lateral margins of the wall portions being joined by semi-circular portions of low radius; the emitter tube, when subject to internal pressure, being expansible into essentially cylindrical contour, the radius of which is essentially identical to the radius of the arched portion; that is, the curvature of the arched portion remains essentially constant from zero to maximum pressure. The arched portion is provided with a series of emitter ports and the internal surfaces of the arched portion surrounding the ports are utilized by the valve elements to form at a predetermined low pressure a series of flush flow discharge passages and to form at a greater pressure a series of drip flow discharge passages.