(げすい)

げすい
noun
sewage, drainage
1. sewage, wastewater
Dirty water that flows from houses and buildings into drains.
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:

CONTRAST:

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.