“Plumbing system” means the water supply and distribution pipes, plumbing fixtures and traps, soil, waste, and vent pipes, sanitary and storm sewers and building drains, including their respective connections, devices, and appurtenances within the premises, and water-treating equipment.
Source:
Section 113865, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=HSC§ionNum=113865..