Abstract
We previously reported that test balls made of less-bounce material was suitable for drainage flow examination, and hardly went into branch pipes. It was found, however, that a few less-bounce test balls of 25mm in diameter stopped at swirling vanes in drainage joints. A drainage flow experiment was carried out on differently-shaped test pieces to select better shapes. All of bigger balls of 35-40mm in diameter and almost all of flat ovals successfully went through drainage joints as well as horizontal pipes.
