drainage

v. 排水
n. 排水系统,污水

The drainage system has been aged.

排水系统已经老化了。

The city was even equipped with a drainage system, for a great many clay pipes were found beneath the narrow streets.

这座城市甚至还敷设过排水系统，因为在窄窄的街道底下发现了许多陶土制的管道。