Which statement correctly defines a Non-Transient Non-Community Water System (NTNCWS)?

• A. A PWS that serves all year-round to a city.
• B. A PWS that regularly supplies at least 25 of the same people at least 6 months per year but not year-round.
• C. A PWS that serves only schools.
• D. A PWS that only uses bottled water.

Answer: (B)

A Non-Transient Non-Community Water System is defined by serving a stable group of people, at least 25 of them, for a substantial part of the year but not year-round. The “non-transient” part means the same people are served regularly, and “non-community” means it isn’t a community system serving the public at a fixed location year-round.

The statement that matches this definition is the one that says the system regularly serves at least 25 of the same people for at least six months per year, but not year-round. That combination—minimum population, fixed group, and half-year duration—is exactly what identifies an NTNCWS.

The other descriptions don’t fit as cleanly: a system serving a city year-round describes a community water system; a system that serves only schools can meet the 25-and-six-month criterion but isn’t the defining characteristic on its own; and a system that uses only bottled water isn’t considered a public water system in the same sense.