The board shall promulgate and enforce state primary drinking water regulations that at no time shall be less stringent than the complete, current interim or revised national primary drinking water regulations. State primary drinking water regulations shall apply to each public water system in the state, except those which meet all the following:

1. (1) Consist only of distribution and storage facilities and which do not have any collection and treatment facilities;
2. (2) Obtain all their water from, but are not owned or operated by, a public water system to which such regulations apply;
3. (3) Do not sell water to any person; and
4. (4) Are not carriers which convey passengers in interstate commerce.

(Acts 1977, No. 805, p. 1389, §4.)