| 摘要 |
The expanded, female end of an elliptical drain or sewerpipe is provided with an installation alignment mark on the inner edge surface or on the end face of the pipe to designate at least one major cross-sectional axis point or intersection. The pipe is installed with such internal alignment mark on the bottom side of the pipe in a ground trench whereby the mark is not burried in or hidden by the trench bottom earth, and is cooperable with a second internal or external alignment mark on the opposite side of the pipe end to facilitate the accurate vertical orientation of the major axis with the aid of a plumb line or the like. |
