Abstract: A sealing ring made of an elastomeric readily flowable incompressible material utilized for perfecting a seal between the interior surface of a coupling sleeve and the crest of a rib of a section of corrugated plastic pipe, the sealing ring having a generally flat annular body which in its free form has its major cross-sectional series of axially extending ribs, one of which is located on the inner diametrical surface of the ring for securing the ring within the valley between adjacent ribs on the corrugated pipe, a second rib located on the outer circumferential surface of the ring for primarily sealing between the coupling sleeve and the proximal area of the crest of a rib of the corrugated pipe against infiltration of external fluids and solids, and an intermediate rib for primarily sealing between the coupling sleeve and the distal area of the crest of a rib of the corrugated pipe against the escape of fluids and solids flowing therethrough.