Md. Code, Environment § 9–408

(a) Except as provided in subsection (b) of this section, and subject to § 9-409 of this subtitle, State primary drinking water regulations shall apply to every public water system in this State.

(b) The State primary drinking water regulations do not apply to a public water system that:

(1) Consists only of distribution and storage facilities, and does not have any collection and treatment facilities;

(2) Obtains all of its water from, but is not owned or operated by, a public water system to which the State primary drinking water regulations apply;

(3) Does not sell water to any person; and

(4) Is not a carrier that conveys passengers in interstate commerce.