(げすい)

げすい
noun
sewage, drainage
1. sewage, wastewater
Dirty water that flows from houses and buildings into drains.
下水(げすい)処理場(しょりじょう)汚水(おすい)きれいにされる。
Wastewater is cleaned at the sewage treatment plant.
下水(げすい)(にお)する
It smells like sewage.
Sewage flowed into the river.
Sewage treatment is necessary.
Wastewater is discharged from the factory.
2. sewer, drainage system
The system of pipes and channels that carries away sewage.
下水(げすい)()まっている
The sewer is clogged.
Construction of the sewer system has begun.
Repair the sewer pipes.
下水(げすい)(あふ)れた
The sewer overflowed.

下水(げすい) covers both the wastewater itself (sense 1) and the system that carries it away (sense 2). A compound of () (lower) + (すい) (water).

COMMON COLLOCATIONS:

  • 下水道(げすいどう): sewer system
  • 下水(げすい)処理(しょり): sewage treatment
  • 下水(げすい)処理場(しょりじょう): sewage treatment plant
  • 下水(げすい)工事(こうじ): sewer construction
  • 下水(げすい)()まる: sewer gets clogged

CONTRAST:

  • 上水(じょうすい): clean water supply (the opposite — (じょう) means "upper/clean")
  • 上水道(じょうすいどう): water supply system

NOTE:
下水道(げすいどう) (with (どう)) specifically means the sewer system/infrastructure, while 下水(げすい) alone can mean both the water and the system.