Patent ID: 6941972

Claim:
A corrugation comprising: a radially inner wall circumferentially surrounding an axis and defining an inner cavity configured to conduct a liquid axially through said inner cavity; and a radially outer wall overlying said inner wall, said outer wall adjoining said inner wall so as to form an outer cavity bounded by said inner and outer walls and separated from said inner cavity by said inner wall and closed to the outside by said outer wall; said inner wall having first and second openings providing fluid communication between said inner and outer cavities such that said corrugation provides a reservoir for the liquid conducted through said inner cavity; said corrugation having a predetermined installed orientation defined by a designated bottom end of said corrugation; said second opening being located higher than said first opening in said installed orientation of said corrugation; and said corrugation being centered on said axis and, in said installed orientation of said corrugation, said first opening is located at an angle of about 35 to about 55 degrees below said axis, and said second opening is located at an angle of about 35 to about 55 degrees above said axis.