This is the 7234th most frequent Japanese word.
下水道
Sewer system.
Here, "下水道" refers to an advanced sewage system structure as a public utility.
その町には新しい下水道システムが導入されました。
A new sewage system was introduced in that town.
In this sentence, "下水道" indicates the physical infrastructure requiring maintenance.
下水道のメンテナンスは定期的に行う必要があります。
Maintaining the sewage system needs to be done regularly.
Here, "下水道" is used to describe the system's capacity being affected by environmental factors.