What distinguishes a non-transient non-community water system from other systems?

A non-transient non-community water system is identified by its capacity to serve at least 25 people for at least six months of the year. This type of system provides water to a stable population that is not permanent, such as employees of a company or residents of a housing complex that is not classified as a community water system. In contrast, transient water systems serve temporary or seasonal populations, and community systems serve residents of a specific area who have a consistent and permanent customer base. Thus, the defining characteristic of a non-transient non-community water system rests on its ability to cater to a regular, albeit non-permanent, group of users over an extended period, which is why this answer is correct.