Department of
Environmental Quality

What is a Public Water System?

A Public Water System (PWS) is a system for the provision of water to the public for human consumption through pipes or other constructed conveyances, if such system has at least 15 service connections or regularly serves an average of at least 25 individuals at least 60 days out of the year. Idaho currently has ±1,960 public water systems.

A public water system can be one of three types:

Community Water System

Serves at least 15 service connections or 25 people year round in their primary residences (e.g., most cities and towns, apartments, and mobile home parks with their own water supplies). About 38% of Idaho's public water systems are classified as community water systems.

Non-transient Non-community Water System (NTNCWS)

Serves at least 25 of the same persons over six months per year (e.g., schools, churches, nursing homes, and factories, and hospitals that have their own water source). Almost 12% of Idaho's public water systems fit into this category.

Transient Non-community Water Systems (TNCWS)

Serves an average of at least 25 persons (but not the same 25) less than six months per year (e.g., campgrounds or highway rest stops that have their own water source). About half of Idaho's public water systems meet these criteria.