Dirty Water, Filthy Water, Sewage
noun
Dirty water is dirty water. Gross. Could also be sewage. Even grosser.
おすい
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
雪の日に汚水の配管が詰まってしまいました。
Sewage pipes get blocked on snow days.