International Building Code 101.4.4
Plumbing. The provisions of the International
Plumbing Code shall apply to the installation, alteration,
repair and replacement of plumbing systems, including
equipment, appliances, fixtures, fittings and appurtenances,
and where connected to a water or sewage system and all
aspects of a medical gas system. The provisions of the International
Private Sewage Disposal Code shall apply to private
sewage disposal systems.