A specialty classification that involves installation, maintenance, and repair of commercial and residential plumbing systems. The scope of work includes sanitary drainage or storm drainage facilities; venting systems; public or private water supply systems; septic tanks; drainage and supply wells; swimming pool piping; and irrigation systems. The scope of work also includes installation, maintenance, repair, alteration or extension of air-piping, vacuum line piping, oxygen line piping, nitrous oxide piping, and all other related medical gas systems; fire line standpipes and fire sprinklers, ink and chemical lines; fuel oil and gasoline piping and tank and pump installation except bulk storage plants; and pneumatic control piping systems. Includes any excavation work incidental thereto. This classification does NOT include fuel gas or boiler systems.