Indiana Code Title 25. Professions and Occupations § 25-28.5-1-32

(1) Contractors in work on bridges, roads, streets, highways, railroads, or utilities and services incidental to the work.

(2) An authorized employee of the United States, the state, or a political subdivision of the state if the employee does not profess to be for hire and is acting within the scope of the employee's employment.

(3) An officer appointed by a court when the officer is acting within the scope of the officer's office as defined by law or court order.  When construction projects are not underway at the time of the appointment of the officer by the court, and the nature of the officer's appointment requires that plumbing must be done, the officer must employ or contract with a registered plumbing contractor or journeyman plumber.

(4) Public utilities with respect to construction, maintenance, and development work performed by their own forces and incidental to their business.

(5) The owner occupant of a dwelling of eight (8) or less residential units when the owner occupant is installing, altering, or repairing the plumbing system of the residential units.

(6) Construction, alteration, improvement, or repair of a plumbing system, located on a site, the title of which is in the name of the United States of America, or to construction, alteration, improvement, or repair on a project where federal law supersedes this article.

(7) An individual who is employed or acts as a maintenance person at the individual's place of employment.

(8) Farmsteads, except for buildings built on the farmstead for the purpose of public or commercial use.

(9) A sewer contractor, sewage disposal contractor, or an excavation contractor or utility contractor who generally engages in the business of installing, altering, or repairing sewers, private or public sewage disposal systems, and water distribution or drainage lines outside the foundation walls of a building.