Abstract: An adaptor for forming a branch in a conduit is shaped and dimensioned to slide onto a cylindrical conduit. The adaptor includes a collar having an outer generally circumferentially extending wall, end walls and a cylindrical passage extending between the end walls. The passage has an inner wall and an opening at each end, and spaced resiliently deformable sealing means adjacent each opening. The sealing means is positioned to provide a seal between the collar and the cylindrical conduit when the adaptor is slidingly engaged with the cylindrical conduit. The collar includes at least one fluid flow passage extending between the outer wall and the inner wall.