Haw. Rev. Stat. § 340F-2

The board shall classify all public water systems, water treatment plants, and distribution systems, and shall define the terms "water treatment plant" and "distribution system". The classifications shall take due regard to size, complexity, and type of the water treatment facility or distribution system, character of water to be treated or distributed, and other physical conditions affecting such water treatment plants and distribution systems, and the skill, knowledge, and experience required of an operator.