| 摘要 |
PROBLEM TO BE SOLVED: To provide a standpipe for sewage allowing easy and quick inspection of an abrasion condition produced by use over a long time. SOLUTION: A spiral guide plate 5A forming a spiral guide path in the standpipe for sewage is provided with a colored layer 11 layered in the position matching the thickness of a friction margin in a base material constituting the spiral guide path in the standpipe for sewage.
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